qunit: Prepare testrunner for QUnit 2
* Nested modules:
- Support for Sinon extension was fixed by Ib17bbbef45b2bd.
- Support for Fixture extension was still broken, masked by the use
of a local variable that made the handler not fail when setup ran twice
in a row. Fixed using the same moduleStack.length check.
- Add regression test.
* beforeEach/afterEach:
- Added in 1.16, with compat for setup/teardown.
Our wrapper adds its own setup/teardown, and preserves any original one.
However, it didn't account for beforeEach/afterEach, so it ends up
sending both but only one is used.
- Fix to support both on the incoming localEnv object, and also switch
our wrapper to use beforeEach/afterEach in prep for QUnit 2.0.
- Fix our wrappers to preserve return value since QUnit 2 allows beforeEach
and afterEach hooks to be asynchronous by returning a Promise, similar
to how one can do from QUnit.test().
- Add regression test.
* Centralise makeSafeEnv logic
- We always create our own env object to pass to orgModule().
Document why this is (to avoid recursion).
- Add regression test.
* Custom assertion methods:
- Use this.pushResult instead of the deprecated QUnit.push() method.
This also improves the in-browser reporting of errors by properly
supporting 'negative' results for notHtmlEqual reporter.
Bug: T170515
Change-Id: If4141df10eae55cbe8a5ca7a26707be1cd7b9217