Remove legacy esp8266 toolchain support

[mikee47]

This PR removes legacy toolchain cruft from the framwork.

• Old esp8266 libc support not required. All esp-quick-toolchain compiler versions use newlib.
• Change compiler version check to error. Code won't work with old toolchains.
• Remove use of GCC_VERSION_COMPATIBLE from UPnP library. Framework does check, libaries don't need to.

[what-the-diff]

PR Summary

• Added Flag for Patched GDB
  An additional flag titled GDBSTUB_GDB_PATCHED was inserted into APP_CFLAGS. This aids in the debugging process with a more sophisticated set of capabilities.

• Inclusion of Extra Libraries
  The variable EXTRA_LIBS in Sming/Arch/Esp8266/Components/libc/component.mk has been adjusted to include stdc++. This inclusion expands the codebase with added functionalities available in the stdc++ library.

• Removal of Redundant Files
  Several non-essential files, namely, libmicroc.a, libmicrogcc.a, and libsetjmp.a, have been removed from the Components/libc/lib directory, aiding in decluttering the project repository.

• File Rename for Better Clarity
  The file libc_replacements.c previously under the newlib directory, has been renamed and relocated directly under the src directory, making it simple to locate.

• Elimination of Outdated Files
  Five outdated files, namely under the oldlib directory have been deleted - README.rst, pgmspace.c, strcspn.c, strerror.c, and strspn.c. This step would decrease unnecessary elements from the codebase.

• Version Compatibility Check
  The GCC_VERSION_COMPATIBLE variable in Sming/build.mk has been adjusted to accommodate potential changes in the version of GCC being used.

• Improved Repository Fetch
  The fetch command in Linux's getting started documentation has been enhanced to include the URL of the Sming repository for straightforward clone operations.