fix(eslint-plugin): [no-unnecessary-conditionals] Handle comparison of generics and loose comparisons with undefined values

[avocadowastaken]

Follow-up for #2123 (comment)

[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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[codecov]

Codecov Report

Merging #2152 into master will decrease coverage by 0.02%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #2152      +/-   ##
==========================================
- Coverage   93.56%   93.53%   -0.03%     
==========================================
  Files         171      171              
  Lines        7811     7814       +3     
  Branches     2229     2228       -1     
==========================================
+ Hits         7308     7309       +1     
- Misses        244      245       +1     
- Partials      259      260       +1     

Flag	Coverage Δ
#unittest	93.53% <100.00%> (-0.03%)	⬇️

Impacted Files	Coverage Δ
...slint-plugin/src/rules/no-unnecessary-condition.ts	97.31% <100.00%> (+0.05%)	⬆️
packages/eslint-plugin/src/util/types.ts	81.21% <0.00%> (-1.22%)	⬇️

[bradzacher]

lgtm - thanks for the follow up!