test: use RTL in the version selector tests

[erikian]

Another step towards #1408. I've added a couple of changes on top of just migrating the tests to RTL (open to feedback if any of them are a bad idea):

• extracted some duplicate version mocking logic to a separate file
• created a helper function to render the VersionSelect component - I didn't do it in a beforeEach block because we only need to render the whole component in one test
• added a missing test for the renderVersionContextMenu component

I've also included the testMatch change from #1434 just so the RTL tests will run on CI for this PR. This means that #1434 should land first to keep things separate and to prevent it from becoming an empty changeset.

[coveralls]

coverage: 87.213% (+0.2%) from 87.009%
when pulling 708e7fa on test/version-selector-rtl
into 1ec5c07 on main.

[ckerr]

Looks like this was approved a a couple of months ago but not merged.

@erikian is this PR still something that should be merged; and if so, could you update the PR to resolve the conflicts that have built up in the interim? 😸

[erikian]

@ckerr I'll try to get this PR rebased later this week, thanks for the reminder!