feat(eslint-plugin): [prefer-readonly-parameter-types] add ignoreInferredTypes option

[eyelidlessness]

This PR addresses part of #2079. I'm not sure whether I should mark this as fixes, since there's discussion of other wants. So I'll leave that determination up to the reporter and maintainers).

This introduces an ignoreInferredTypes option for prefer-readonly-parameter-types, which if true ignores errors on parameters with no explicit type parameter. This may be useful for cases where an external dependency specifies mutable parameter types, e.g. for parameters in callbacks.

[typescript-eslint]

Thanks for the PR, @eyelidlessness!

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[eyelidlessness]

Dang, I knew it was risky for me to make that second commit without rerunning lint etc locally. Fixes incoming!

[codecov]

Codecov Report

Merging #2668 into master will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #2668   +/-   ##
=======================================
  Coverage   92.83%   92.83%           
=======================================
  Files         294      294           
  Lines        9666     9669    +3     
  Branches     2711     2712    +1     
=======================================
+ Hits         8973     8976    +3     
  Misses        327      327           
  Partials      366      366           

Flag	Coverage Δ
#unittest	92.83% <100.00%> (+<0.01%)	⬆️

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

Impacted Files	Coverage Δ
...lugin/src/rules/prefer-readonly-parameter-types.ts	100.00% <100.00%> (ø)

[eyelidlessness]

Okay, so I was looking at the code coverage report to try to see why it was such a significant reduction, and... discovered that not only had I implemented this incorrectly... I also had gotten false positives in the tests because apparently eslint-disable is infectious. So that's probably not the right approach here, and I'm unsure how to proceed, because the setup requires an erroneous precondition. I think what I'll probably do is put this PR into draft mode for now and spend some time looking through the codebase for prior art.

[bradzacher]

nice and simple - thanks for this option, should save people a lot of pain.