Update the Babel plugin to remove empty class constructors

[Snuffleupagus]

To avoid useless class constructors we utilize the ESLint no-useless-constructor rule, which works well in most cases.
The exception is when a constructor includes pre-processor statements that make it conditionally empty, note e.g. how the following source code:

pdf.js/src/display/editor/tools.js

Lines 61 to 67 in b676540

	constructor() {
	if (typeof PDFJSDev !== "undefined" && PDFJSDev.test("TESTING")) {
	Object.defineProperty(this, "reset", {
	value: () => (this.#id = 0),
	});
	}
	}

is transformed into (in that case for the MOZCENTRAL build):
https://searchfox.org/mozilla-central/rev/dbd654fa899a56a6a2e92f325c4608020e80afae/toolkit/components/pdfjs/content/build/pdf.mjs#1829

Hence it seems like a good idea to extend the Babel plugin to remove class constructors that become empty during building.

/cc @nicolo-ribaudo

[nicolo-ribaudo]

I can work on this.

Do we have cases in which we also need to remove subclass constructors like the following?

class A extends B {
  constructor(...args) { super(...args) }
}

[Snuffleupagus]

I can work on this.

Thank you!

Do we have cases in which we also need to remove subclass constructors like the following?

class A extends B {
  constructor(...args) { super(...args) }
}

That exact pattern should already be caught by no-useless-constructor, at least I think so.