feat: update class-methods-use-this for class static blocks

[mdjermanovic]

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• I have read the contributing guidelines.

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

[ ] Documentation update
[ ] 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 #15016, fixes class-methods-use-this.

What changes did you make? (Give an overview)

Updated the class-methods-use-this rule to account for class static blocks.

This only fixes false negatives where use of this in a class static block mistakenly counts as used this in the enclosing context:

/* eslint class-methods-use-this: error */

class A {
    foo () { // false negative, this method does not use `this`.
        return class {
            static {
                this;
            }
        } 
    }
}

The rule still correctly does not require that class static blocks use this.

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