Update: support class fields in func-name-matching (refs #14857)

[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)
[x] Changes an existing rule (template)
[ ] Add autofixing to a rule
[ ] Add a CLI option
[ ] Add something to the core
[ ] Other, please explain:

refs #14857, fixes #14591 (comment)

What changes did you make? (Give an overview)

Updated the func-name-matching rule to:

• ignore assignments to private fields, such as this.#x = function foo() {};, instead of crashing (this is a bug fix).
• check and report class field definitions, e.g. class C { foo = function bar() {}; } (this is an enhancement). Private fields are ignored.

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

[nzakas]

LGTM. I’m unsure if we should include private names or not, but I think it’s fine to roll with this and just see what feedback we get.

[aladdin-add]

LGTM! 💯