cleanup:test: rewrite jest mocks to use jest.mocked

[firestack]

There's more to do, but as an incremental fix, I think this is good enough for 15m of time.

I ran these commands, and then reverted tests that started failing.

, ast-grep run -p '($V as jest.Mock)' -r 'jest.mocked($V)' ./assets/ -U

, ast-grep run -p '($V as jest.Mock<$_>)' -r 'jest.mocked($V)' ./assets/ -i

[github-actions]

Coverage of commit 75c9e70

Summary coverage rate:
  lines......: 93.8% (3220 of 3433 lines)
  functions..: 73.4% (1333 of 1816 functions)
  branches...: no data found

Files changed coverage rate: n/a

Download coverage report

[joshlarson]

I basically just looked through to see if I could find any obvious mistakes, which I couldn't, and also the builds pass.

Thanks for doing this!