Convert fs operations from sync to async

[ijjk]

This converts our sync fs usage to async to help with performance and to allow external resolve functions to be async as well. Noticed the synchronous resolving was taking a big chunk of time while tracing during next build so hopefully this allows us to hook into webpack's resolver and give a good performance boost.

[codecov]

Codecov Report

Merging #236 (1ef8c19) into main (95f0a04) will increase coverage by 0.19%.
The diff coverage is 88.72%.

❗ Current head 1ef8c19 differs from pull request most recent head e04da34. Consider uploading reports for the commit e04da34 to get more accurate results

@@            Coverage Diff             @@
##             main     #236      +/-   ##
==========================================
+ Coverage   80.11%   80.30%   +0.19%     
==========================================
  Files          13       13              
  Lines        1438     1447       +9     
  Branches      538      539       +1     
==========================================
+ Hits         1152     1162      +10     
+ Misses        114      113       -1     
  Partials      172      172              

Impacted Files	Coverage Δ
src/resolve-dependency.ts	69.81% <77.77%> (ø)
src/analyze.ts	86.49% <89.47%> (-0.08%)	⬇️
src/node-file-trace.ts	81.22% <93.33%> (+1.31%)	⬆️
src/utils/static-eval.ts	82.95% <95.65%> (ø)
src/utils/sharedlib-emit.ts	66.66% <100.00%> (ø)
src/utils/special-cases.ts	89.28% <100.00%> (ø)

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[styfle]

I think you should add a test for async usage too 🙂

[styfle]

Nice work, thanks! 🎉