Add Lint/PercentStringArray and Lint/PercentSymbolArray cops

[owst]

Adds a new cop Lint/PercentString cop:

  # This cop checks for colons and commas in %i, e.g.
  #
  #   `%i(:foo, :bar)`
  #
  # and quotes and commas in %w, e.g.
  #
  #   `%w('foo', "bar")`
  #
  # in both cases, it is more likely that the additional characters are
  # unintended (for example, mistranslating an array of literals to percent
  # string notation) rather than meant to be part of the resulting
  # strings/symbols.

I recently made this mistake in my work code, and it was only due to a keen-eyed reviewer (@Qlexander - thanks 👍) that I avoided introducing a bug, so I think Rubocop can help us out here.

---

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[owst]

Because of $, on line 26

[bbatsov]

I wonder if we can account account for cases like these.

[joehorsnell]

Looks good @owst - only minor comments would be to a) potentially call it Lint/PercentArrayLiteral since they are literal array rather than string syntax and b) maybe have two linters, one for the string array and the other for the symbol array.

[bbatsov]

@joehorsnell Great remarks. Probably I'd go with different cops.

[bbatsov]

Guess the cop could account for cases like this one.

[owst]

About naming - the literals ruby doc refers to them as Percent Strings

[owst]

@bbatsov separate cops - done!

[bbatsov]

Has to be rebased.

[owst]

@bbatsov - done!