Breaking: no-dupe-class-members checks some computed keys (fixes #12808)

[mdjermanovic]

Prerequisites checklist

• I have read the contributing guidelines.
• The team has reached consensus on the changes proposed in this pull request. If not, I understand that the evaluation process will begin with this pull request and won't be merged until the team has reached consensus.

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

[X] Changes an existing rule #12808

What changes did you make? (Give an overview)

no-dupe-class-members was ignoring all computed keys.

After this PR, this rule will also check those class members for which astUtils.getStaticPropertyName returns a string value. This is new default behavior.

/*eslint no-dupe-class-members: ["error"]*/

class A {

  ["a"](){}
  ["a"](){} // error

  ["b"](){}
  b(){} // error

  "c"(){}
  [`c`](){} // error
  
  [123](){}
  123(){} // error

}

The rule will still ignore computed keys with values that are not statically known:

/*eslint no-dupe-class-members: ["error"]*/

class A {

  [a](){}
  [a](){} // no error

}

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

[kaicataldo]

LGTM, thanks! Appreciate the extensive test suite!

[yeonjuan]

LGTM! 👍

[btmills]

In today's TSC meeting, we added this to the v7.0.0 release!