Create bugfix plugin for classes in computed keys in Firefox

[nicolo-ribaudo]

Q	A
Fixed Issues?	Fixes #16379
Patch: Bug Fix?	Y
Major: Breaking Change?
Minor: New Feature?
Tests Added + Pass?	Yes
Documentation PR Link	babel/website#2885
Any Dependency Changes?
License	MIT

This PR adds a plugin to compile

class A {
  #x = 42;
  [class {}];
} 

to

class A {
  #x = 42;
  [(() => class {}).call()];
} 

in Firefox, so that it doesn't throw a syntax error.

[nicolo-ribaudo]

For tiny browser bugs this is probably easier than having to go through compat-table.

[babel-bot]

Build successful! You can test your changes in the REPL here: https://babeljs.io/repl/build/56589

[nicolo-ribaudo]

We need to add .call() here to prevent Terser from undoing the work done by this plugin: terser/terser#1514

[liuxingbaoyu]

I think this is fine, because it is possible that more than just terser will do this (or may do so in the future).

[JLHwung]

Awesome.

[liuxingbaoyu]

👍

[nicolo-ribaudo]

I'm preparing a docs PR.