fix(typescript-estree): improve comment parsing code

[bradzacher]

Fixes #1114

Potentially could (fix) #1042 as well.

I figured that this was a solved problem, and it turns out it was.
tsutils had a function to do it.
It invovles adding a dep, but I figured it was better? I considered copying it but there are several hundred lines of code to copy, and we'd have ensure we honour the licence etc.

[typescript-eslint]

Thanks for the PR, @bradzacher!

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[codecov]

Codecov Report

Merging #1120 into master will decrease coverage by 0.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #1120      +/-   ##
==========================================
- Coverage      94%   93.98%   -0.02%     
==========================================
  Files         120      120              
  Lines        5234     5185      -49     
  Branches     1450     1438      -12     
==========================================
- Hits         4920     4873      -47     
  Misses        178      178              
+ Partials      136      134       -2

Impacted Files	Coverage Δ
packages/typescript-estree/src/node-utils.ts	97.59% <ø> (-0.14%)	⬇️
packages/typescript-estree/src/convert-comments.ts	100% <100%> (+3.7%)	⬆️