fix(eslint-plugin): [no-unnecessary-condition] handle comparison of any, unknown and loose comparisons with nullish values

[avocadowastaken]

, unknown and nullish values (closes #2113)

[typescript-eslint]

Thanks for the PR, @umidbekkarimov!

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!

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[avocadowastaken]

I needed that to have access to isReceiver option.

[codecov]

Codecov Report

Merging #2123 into master will increase coverage by 0.02%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #2123      +/-   ##
==========================================
+ Coverage   93.42%   93.44%   +0.02%     
==========================================
  Files         171      171              
  Lines        7755     7755              
  Branches     2215     2217       +2     
==========================================
+ Hits         7245     7247       +2     
+ Misses        244      243       -1     
+ Partials      266      265       -1     

Flag	Coverage Δ
#unittest	93.44% <100.00%> (+0.02%)	⬆️

Impacted Files	Coverage Δ
...slint-plugin/src/rules/no-unnecessary-condition.ts	96.96% <100.00%> (ø)
packages/eslint-plugin/src/util/types.ts	82.42% <0.00%> (+1.21%)	⬆️

[bradzacher]

LGTM - thanks for doing this!

[Retsam]

It's niche, but we might want similar "NULLISH" handling for the == undefined case, otherwise the error will false positive on code like:

function foo(x: string | null) {
    if(x == undefined) {}
}