Browser: improve 'bdd' import for bundlers

[juergba]

Description

History: #4746

Above PR proved to be too restrictive as it's no longer possible to do ES6 style import { describe, it } from 'mocha' while using bundlers.

Description of the Change

browser-entry.js: push all bdd functions from global to mocha.

We have conflicts between global.setup (tdd version of beforeEach hook) and mocha.setup(browser setup), and therefore we don't copy the tdd functions to mocha. The tdd interface has never/won't be available for ES6 style import.

At the time of copying the bdd functions are undefined, nevertheless bundlers seem to rely on those lines. The exact logic remained unclear to me.

Applicable issues

closes #4763

[juergba]

cc @apellerano-pw @PaperStrike

[apellerano-pw]

Thank you, @juergba and @PaperStrike ! 🎉

[PaperStrike]

Actually I'm still confused how it works...

As in #4746, I'm using playwright-test (which uses esbuild internally) to run mocha tests and the only way to achieve import { describe, it } from 'mocha' is the one copy from Mocha.

Since import { describe, it } from 'mocha' never works in my case and the algorithm (to understand and to support all bundlers) seems quite complex, merging this seems to be the best choice. 👍
(Personally I'm looking forward to the ESM mocha. 👀)

[juergba]

Personally I'm looking forward to the ESM mocha.

Yes, but I'm unsure about the implications, yet.
Will we need globals anymore? I guess no, because a module has its own scope, but Mocha uses globals ever since.
There still remains the conflict on setup(), so evtl. we will need import { describe, it } from 'mocha.bdd'.