✨ New Universal.WhiteSpace.CommaSpacing sniff

[jrfnl]

New sniff to enforce no space before a comma and exactly one space, or a new line, after a comma.
Additionally, the sniff also enforces that the comma should follow the code and not be placed after a trailing comment.

For the spacing part, the sniff makes the following exceptions:

1. A comma preceded or followed by a parenthesis, curly or square bracket.
   These will not be flagged to prevent conflicts with sniffs handling spacing around braces.
2. A comma preceded or followed by another comma, like for skipping items in a list assignment.
   These will not be flagged.
3. A comma preceded by a non-indented heredoc/nowdoc closer.
   In that case, unless the php_version config directive is set to a version higher than PHP 7.3.0, a new line before will be enforced to prevent parse errors on PHP < 7.3.

The sniff has a separate error code for when a comma is found with more than one space after it, followed by a trailing comment.
That way trailing comment alignment can be allowed by excluding that error code.

Additionally, the sniff uses modular error code suffixes for select situations, like *InFunctionDeclaration, *InFunctionCall, to allow for preventing duplicate messages if another sniff is already handling the comma spacing.

Includes raising the minimum PHPCSUtils version to 1.0.8 to prevent running into a particular bug in the SpacesFixer.

Note: a few of the test files will only run when the tests are run on PHP 7.3+ as the tests involve PHP 7.3+ flexible heredoc/nowdoc tokens, which is the one syntax which PHPCS cannot polyfill in the Tokenizer.

Includes fixers.
Includes unit tests.
Includes documentation.
Includes metrics.