fix(scope-manager): fallback to lib 'esnext' or 'es5' when ecma version is unsupported

[gcangussu]

Fixes #2468

• Test on real code base
• Write automated tests

[typescript-eslint]

Thanks for the PR, @gcangussu!

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 #2474 into master will increase coverage by 0.02%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #2474      +/-   ##
==========================================
+ Coverage   92.80%   92.82%   +0.02%     
==========================================
  Files         289      289              
  Lines        9294     9294              
  Branches     2599     2600       +1     
==========================================
+ Hits         8625     8627       +2     
+ Misses        322      321       -1     
+ Partials      347      346       -1     

Flag	Coverage Δ
#unittest	92.82% <100.00%> (+0.02%)	⬆️

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

Impacted Files	Coverage Δ
packages/scope-manager/src/analyze.ts	76.92% <100.00%> (+7.69%)	⬆️

[bradzacher]

LGTM - thanks for doing this