fix(eslint-plugin): [return-await] do not auto-fix when type is any/unknown

[thomasmichaelwallace]

Resolves #2598

Specifically tadhgmister's solution:

If it detected that the value is type any and make a suggestion instead of a fix would that be satisfactory? That way it still gives a warning and IDE has quick fix but the --fix command doesn't remove your await?

[typescript-eslint]

Thanks for the PR, @thomasmichaelwallace!

typescript-eslint is a 100% community driven project, and we are incredibly grateful that you are contributing to that community.

The core maintainers work on this in their personal time, so please understand that it may not be possible for them to review your work immediately.

Thanks again!

---

🙏 Please, if you or your company is finding typescript-eslint valuable, help us sustain the project by sponsoring it transparently on https://opencollective.com/typescript-eslint. As a thank you, your profile/company logo will be added to our main README which receives thousands of unique visitors per day.

[codecov]

Codecov Report

Merging #2671 into master will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #2671   +/-   ##
=======================================
  Coverage   92.78%   92.78%           
=======================================
  Files         294      294           
  Lines        9676     9680    +4     
  Branches     2713     2715    +2     
=======================================
+ Hits         8978     8982    +4     
  Misses        330      330           
  Partials      368      368           

Flag	Coverage Δ
#unittest	92.78% <100.00%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
packages/eslint-plugin/src/rules/return-await.ts	95.87% <100.00%> (+0.17%)	⬆️

[thomasmichaelwallace]

Hmm. I'll take a look at the coverage.

[tadhgmister]

While I don't expect people to run into the unknown case as much, since type unknown | Promise<unknown> collapses to just unknown and is therefore not considered await-able it is definitely desirable to also do suggestion for unknown types.

[bradzacher]

nice and simple. Thanks for fixing this.