Make sinon.stub() mock implementation when nothing is returned (& other tweaks)

[danbeam]

cc @lencioni @catc

In some recent PRs I noticed that sinon.stub(a, b) is transformed into jest.spyOn(a, b).mockClear() but it also needs a .mockImplementation() in the general case (when there's not a .return() or .returnArg()). So I've added that.

Additionally, I read sinon's doc on stub() and spy() and we don't need/implement stub(a) (which mocks all keys in the object) so I'm marking that as unsupported (it's not advised even from sinon's doc).

I added a warning when there's more than 3 arguments (which doesn't seem to be valid, AFAICT).

I also changed jest.fn().mockImplementation(...) to just jest.fn(...) because it's equivalent and shorter.

[codecov]

Codecov Report

Merging #291 (43f869a) into main (93d99e0) will increase coverage by 0.04%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #291      +/-   ##
==========================================
+ Coverage   92.18%   92.22%   +0.04%     
==========================================
  Files          26       26              
  Lines        1842     1852      +10     
  Branches      381      385       +4     
==========================================
+ Hits         1698     1708      +10     
  Misses        102      102              
  Partials       42       42              

Impacted Files	Coverage Δ
src/transformers/sinon.ts	87.31% <100.00%> (+0.65%)	⬆️

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[skovhus]

This is awesome! Thanks for fixing this. 👏