feat(eslint-plugin): sync getFunctionHeadLoc implementation with upstream

[bradzacher]

Splitting this out of #6457 to better focus the PR.
Syncs the utility from upstream giving us better coverage and alignment with ESLint core.

[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!

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✅ Successfully ran 35 targets

• nx test eslint-plugin --coverage=false
• Node 20 - nx test eslint-plugin
• Node 16 - nx test eslint-plugin --coverage=false
• Node 20 - nx test visitor-keys
• Node 20 - nx run types:build
• Node 20 - nx test eslint-plugin-tslint
• Node 20 - nx test type-utils
• Node 20 - nx test eslint-plugin-internal
• Node 20 - nx test utils
• Node 20 - nx test typescript-estree
• Node 20 - nx test repo-tools
• Node 20 - nx test scope-manager
• Node 16 - nx test visitor-keys --coverage=false
• Node 16 - nx run types:build
• Node 20 - nx test parser
• Node 20 - nx test ast-spec
• Node 20 - nx test rule-schema-to-typescript-types
• nx run-many --target=typecheck --parallel
• nx run types:build
• nx run-many --target=lint --parallel
• nx test typescript-estree --coverage=false
• Node 16 - nx test parser --coverage=false
• Node 16 - nx test eslint-plugin-tslint --coverage=false
• Node 16 - nx test typescript-estree --coverage=false
• Node 16 - nx test utils --coverage=false
• Node 16 - nx test ast-spec --coverage=false
• Node 16 - nx test repo-tools --coverage=false
• Node 16 - nx test rule-schema-to-typescript-types --coverage=false
• Node 16 - nx test eslint-plugin-internal --coverage=false
• nx run integration-tests:test
• Node 16 - nx test scope-manager --coverage=false
• nx test eslint-plugin-tslint --coverage=false
• Node 16 - nx test type-utils --coverage=false
• nx test eslint-plugin-internal --coverage=false
• nx run-many --target=build --parallel --exclude=website --exclude=website-eslint

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[codecov]

Codecov Report

Merging #7260 (be95293) into main (e5d668c) will increase coverage by 0.00%.
The diff coverage is 96.55%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #7260   +/-   ##
=======================================
  Coverage   87.47%   87.48%           
=======================================
  Files         379      379           
  Lines       13234    13250   +16     
  Branches     3907     3911    +4     
=======================================
+ Hits        11577    11592   +15     
  Misses       1279     1279           
- Partials      378      379    +1     

Flag	Coverage Δ
unittest	87.48% <96.55%> (+<0.01%)	⬆️

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

Impacted Files	Coverage Δ
...kages/eslint-plugin/src/util/getFunctionHeadLoc.ts	96.66% <96.55%> (-3.34%)	⬇️

[JoshuaKGoldberg]