Fix build breaks

[weswigham]

1. Mocha updated and no longer ships a ms implementation itself, instead it uses the ms package. Now we do in our mocha output, too. In addition, it now only sets up the hooks for generate a .stats object in its .run method (which we don't call, as it sets up a bunch of things we don't need or want), so we need to initialize stats generation ourselves.

2. Seems like Remove diagnostic dependent output in structuredTypeRelatedTo #29817 was opened during the period where we weren't self-testing on CI 😢 This fixes the new strict function type errors identified in watchUtilities by that change (which previously went silently unheard due to the structural fallback & diagnostic-mode dependence of the check!).