fix: ignore spacing before ] and } in comma-spacing

[mdjermanovic]

Prerequisites checklist

• I have read the contributing guidelines.

What is the purpose of this pull request? (put an "X" next to an item)

[ ] Documentation update
[x] Bug fix (template)
[ ] New rule (template)
[ ] Changes an existing rule (template)
[ ] Add autofix to a rule
[ ] Add a CLI option
[ ] Add something to the core
[ ] Other, please explain:

Fixes #16100

Updates the comma-spacing rule to ignore spacing before ] and spacing before } in order to avoid conflicts with array-bracket-spacing and object-curly-spacing rules.

For example, the current version of comma-spacing reports an error on each of the following lines, but fixing them triggers errors from array-bracket-spacing and object-curly-spacing rules:

/* eslint comma-spacing: "error" */
/* eslint array-bracket-spacing: "error" */
/* eslint object-curly-spacing: "error" */

[a,]; // comma-spacing reports missing space after `,` but fixing it triggers array-bracket-spacing

[a,] = foo; // comma-spacing reports missing space after `,` but fixing it triggers array-bracket-spacing

obj = {a,}; // comma-spacing reports missing space after `,` but fixing it triggers object-curly-spacing

var {a,} = obj; // comma-spacing reports missing space after `,` but fixing it triggers object-curly-spacing

import {b,} from "mod"; // comma-spacing reports missing space after `,` but fixing it triggers object-curly-spacing

Playground link

Note that this rule already ignores spacing after [ (#3392) and spacing before ) (#11295).

What changes did you make? (Give an overview)

• Merged validateCommaItemSpacing into the loop in "Program:exit"() because the logic of what to check and what to ignore was unnecessarily scattered.
• Removed JSXText check. We are checking if it's a comma punctuator token just a line before, so it can't be JSXText.
• Added new checks for ] and }.
• Updated the docs accordingly.

Is there anything you'd like reviewers to focus on?

I also wanted to replace addNullElementsToIgnoreList and all related code with a simple [ token check, but it turned out that the existing logic has possibly unintentional side effects of ignoring spacing between a comment and ending comma of a hole/elision.

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[mdjermanovic]

This was conflicting with array-bracket-spacing option "always" on the right side of ,.

Playground link

[nzakas]

LGTM.