feat(eslint-plugin): [pref-str-starts/ends-with] optional chain support

[bradzacher]

See #1051

I discovered the :matches selector, which saves having to enumerate every combination, which saved a lot of effort.

Was pretty straightforward, just a lot of lines.

[typescript-eslint]

Thanks for the PR, @bradzacher!

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 #1357 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #1357      +/-   ##
==========================================
+ Coverage   94.05%   94.05%   +<.01%     
==========================================
  Files         133      133              
  Lines        5934     5940       +6     
  Branches     1679     1686       +7     
==========================================
+ Hits         5581     5587       +6     
  Misses        186      186              
  Partials      167      167

Impacted Files	Coverage Δ
...ages/eslint-plugin/src/rules/no-require-imports.ts	100% <ø> (ø)	⬆️
...ackages/eslint-plugin/src/rules/prefer-includes.ts	100% <ø> (ø)	⬆️
...plugin/src/rules/prefer-string-starts-ends-with.ts	100% <100%> (ø)	⬆️