test: move help strings to markdown file

[m11o]

issue: #4368

This PR contains bellow contents.

• Remove duplicated expressions 22d1880
• Move help strings to markdown file d6366c4

This command has two util names ( test or [ ). And, the format_usage method replaces {} with a util name. So, we changed USAGE as strings that do not contain {}.
If there are better ideas, please tell me.

before

$ cargo run -- [ --help
Check file types and compare values.

Usage: target/debug/coreutils [ EXPRESSION
           target/debug/coreutils [
           [ EXPRESSION ]
           [ ]
           [ OPTION

Options:
  -h, --help     Print help
  -V, --version  Print version


Exit with the status determined by EXPRESSION.

An omitted EXPRESSION defaults to false.  Otherwise,
EXPRESSION is true or false and sets exit status.  It is one of:

  ( EXPRESSION )               EXPRESSION is true
  ! EXPRESSION                 EXPRESSION is false
  EXPRESSION1 -a EXPRESSION2   both EXPRESSION1 and EXPRESSION2 are true
  EXPRESSION1 -o EXPRESSION2   either EXPRESSION1 or EXPRESSION2 is true

  -n STRING            the length of STRING is nonzero
  STRING               equivalent to -n STRING
  -z STRING            the length of STRING is zero
  STRING1 = STRING2    the strings are equal
  STRING1 != STRING2   the strings are not equal

  INTEGER1 -eq INTEGER2   INTEGER1 is equal to INTEGER2
  INTEGER1 -ge INTEGER2   INTEGER1 is greater than or equal to INTEGER2
  INTEGER1 -gt INTEGER2   INTEGER1 is greater than INTEGER2
  INTEGER1 -le INTEGER2   INTEGER1 is less than or equal to INTEGER2
  INTEGER1 -lt INTEGER2   INTEGER1 is less than INTEGER2
  INTEGER1 -ne INTEGER2   INTEGER1 is not equal to INTEGER2

  FILE1 -ef FILE2   FILE1 and FILE2 have the same device and inode numbers
  FILE1 -nt FILE2   FILE1 is newer (modification date) than FILE2
  FILE1 -ot FILE2   FILE1 is older than FILE2

  -b FILE     FILE exists and is block special
  -c FILE     FILE exists and is character special
  -d FILE     FILE exists and is a directory
  -e FILE     FILE exists
  -f FILE     FILE exists and is a regular file
  -g FILE     FILE exists and is set-group-ID
  -G FILE     FILE exists and is owned by the effective group ID
  -h FILE     FILE exists and is a symbolic link (same as -L)
  -k FILE     FILE exists and has its sticky bit set
  -L FILE     FILE exists and is a symbolic link (same as -h)
  -N FILE     FILE exists and has been modified since it was last read
  -O FILE     FILE exists and is owned by the effective user ID
  -p FILE     FILE exists and is a named pipe
  -r FILE     FILE exists and read permission is granted
  -s FILE     FILE exists and has a size greater than zero
  -S FILE     FILE exists and is a socket
  -t FD       file descriptor FD is opened on a terminal
  -u FILE     FILE exists and its set-user-ID bit is set
  -w FILE     FILE exists and write permission is granted
  -x FILE     FILE exists and execute (or search) permission is granted

Except for -h and -L, all FILE-related tests dereference symbolic links.
Beware that parentheses need to be escaped (e.g., by backslashes) for shells.
INTEGER may also be -l STRING, which evaluates to the length of STRING.

NOTE: Binary -a and -o are inherently ambiguous.  Use 'test EXPR1 && test
EXPR2' or 'test EXPR1 || test EXPR2' instead.

NOTE: [ honors the --help and --version options, but test does not.
test treats each of those as it treats any other nonempty STRING.

NOTE: your shell may have its own version of test and/or [, which usually supersedes
the version described here.  Please refer to your shell's documentation
for details about the options it supports.

after

$ cargo run -- [ --help
Check file types and compare values.

Usage: test EXPRESSION
       test
       [ EXPRESSION ]
       [ ]
       [ OPTION

Options:
  -h, --help     Print help
  -V, --version  Print version

Exit with the status determined by EXPRESSION.

An omitted EXPRESSION defaults to false.
Otherwise, EXPRESSION is true or false and sets exit status.

It is one of:

( EXPRESSION )               EXPRESSION is true
! EXPRESSION                 EXPRESSION is false
EXPRESSION1 -a EXPRESSION2   both EXPRESSION1 and EXPRESSION2 are true
EXPRESSION1 -o EXPRESSION2   either EXPRESSION1 or EXPRESSION2 is true

-n STRING            the length of STRING is nonzero
STRING               equivalent to -n STRING
-z STRING            the length of STRING is zero
STRING1 = STRING2    the strings are equal
STRING1 != STRING2   the strings are not equal

INTEGER1 -eq INTEGER2   INTEGER1 is equal to INTEGER2
INTEGER1 -ge INTEGER2   INTEGER1 is greater than or equal to INTEGER2
INTEGER1 -gt INTEGER2   INTEGER1 is greater than INTEGER2
INTEGER1 -le INTEGER2   INTEGER1 is less than or equal to INTEGER2
INTEGER1 -lt INTEGER2   INTEGER1 is less than INTEGER2
INTEGER1 -ne INTEGER2   INTEGER1 is not equal to INTEGER2

FILE1 -ef FILE2   FILE1 and FILE2 have the same device and inode numbers
FILE1 -nt FILE2   FILE1 is newer (modification date) than FILE2
FILE1 -ot FILE2   FILE1 is older than FILE2

-b FILE     FILE exists and is block special
-c FILE     FILE exists and is character special
-d FILE     FILE exists and is a directory
-e FILE     FILE exists
-f FILE     FILE exists and is a regular file
-g FILE     FILE exists and is set-group-ID
-G FILE     FILE exists and is owned by the effective group ID
-h FILE     FILE exists and is a symbolic link (same as -L)
-k FILE     FILE exists and has its sticky bit set
-L FILE     FILE exists and is a symbolic link (same as -h)
-N FILE     FILE exists and has been modified since it was last read
-O FILE     FILE exists and is owned by the effective user ID
-p FILE     FILE exists and is a named pipe
-r FILE     FILE exists and read permission is granted
-s FILE     FILE exists and has a size greater than zero
-S FILE     FILE exists and is a socket
-t FD       file descriptor FD is opened on a terminal
-u FILE     FILE exists and its set-user-ID bit is set
-w FILE     FILE exists and write permission is granted
-x FILE     FILE exists and execute (or search) permission is granted

Except for -h and -L, all FILE-related tests dereference symbolic links.
Beware that parentheses need to be escaped (e.g., by backslashes) for shells.
INTEGER may also be -l STRING, which evaluates to the length of STRING.

NOTE: Binary -a and -o are inherently ambiguous.
Use 'test EXPR1 && test EXPR2' or 'test EXPR1 || test EXPR2' instead.

NOTE: [ honors the --help and --version options, but test does not.
test treats each of those as it treats any other nonempty STRING.

NOTE: your shell may have its own version of test and/or [, which usually supersedes the version described here.
Please refer to your shell's documentation for details about the options it supports.

[github-actions]

GNU testsuite comparison:

Congrats! The gnu test tests/tail-2/inotify-dir-recreate is no longer failing!

[cakebaker]

Thanks for your PR. Can you please use some markdown lists? The rendered markdown currently looks a bit messy: https://github.com/uutils/coreutils/blob/7b23281b06011ff7838d8c2cab6bb084fdfc46f4/src/uu/test/test.md

[sylvestre]

same here and below

[sylvestre]

Please add * in the other places