feat(eslint-plugin): [no-unnecessary-condition] remove option ignoreRHS

[Retsam]

BREAKING CHANGE:

The 'ignoreRHS' option was an unnecessary part of this lint rule; it forced the user to choose between false-negatives (e.g. if(expr && true)) or false positives return expr && <ReactComponent>.

The new logic only checks the right hand side of a logical operator if the logical expression is in a conditional context: e.g. it's inside an if block, or it's the left hand side of another logical expression.

Fixes #1017.

[typescript-eslint]

Thanks for the PR, @Retsam!

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[Retsam]

A side-effect of this change, checking logical expressions is a bit more fine-grained. Previously if(a && b && c) (with ignoreRHS off) would check the type of c and the type of (a && b) to determine if any part of the condition was unnecessary. Now the types of a, b, and c are checked independently.

This is an assuming that we can detect any unnecessary conditions by looking at a, b and c independently. I believe it's correct, that if a && b or a || b is unnecessary ("unnecessary" means "always truthy" or "always falsy"), then either a or b is unnecessary.

If anyone can come up with a counter-example, where the two independently look necessary, but the combination is unnecessary, I think I can tweak the logic to account for that case.

[codecov]

Codecov Report

Merging #1163 into master will decrease coverage by 1.58%.
The diff coverage is 91.30%.

@@            Coverage Diff             @@
##           master    #1163      +/-   ##
==========================================
- Coverage   95.49%   93.91%   -1.59%     
==========================================
  Files         150      171      +21     
  Lines        6639     7787    +1148     
  Branches     1880     2238     +358     
==========================================
+ Hits         6340     7313     +973     
- Misses        112      217     +105     
- Partials      187      257      +70     

Flag	Coverage Δ
#unittest	93.91% <91.30%> (?)

Impacted Files	Coverage Δ
...es/eslint-plugin/src/configs/eslint-recommended.ts	100.00% <ø> (ø)
packages/eslint-plugin/src/rules/ban-ts-ignore.ts	100.00% <ø> (ø)
...nt-plugin/src/rules/consistent-type-definitions.ts	90.32% <ø> (ø)
...s/eslint-plugin/src/rules/interface-name-prefix.ts	100.00% <ø> (+16.66%)	⬆️
...es/eslint-plugin/src/rules/no-array-constructor.ts	100.00% <ø> (ø)
...ackages/eslint-plugin/src/rules/no-explicit-any.ts	92.85% <0.00%> (-7.15%)	⬇️
...slint-plugin/src/rules/no-unnecessary-qualifier.ts	96.15% <ø> (ø)
...nt-plugin/src/rules/no-untyped-public-signature.ts	100.00% <ø> (ø)
...s/eslint-plugin/src/rules/no-unused-expressions.ts	100.00% <ø> (ø)
...nt-plugin/src/rules/no-unused-vars-experimental.ts	91.48% <ø> (+0.09%)	⬆️
... and 138 more