fix(typescript-estree): better handle canonical paths

[bradzacher]

Whilst investigating #1110, I found that there are some cases where typescript will give us their "canonical path" instead of the actual path.

This is a problem on unix because the canonical path is all lower case, which means we can fail to fire directory updates, because the watcher path doesn't match.

This PR adds a pseudo-nominal type (waiting for the day typescript adds it for real) which ensures (at typecheck time) that the canonical path passed in where required.

[codecov]

Codecov Report

Merging #1111 into master will decrease coverage by 0.02%.
The diff coverage is 89.65%.

@@            Coverage Diff             @@
##           master    #1111      +/-   ##
==========================================
- Coverage   94.09%   94.07%   -0.03%     
==========================================
  Files         120      120              
  Lines        5200     5211      +11     
  Branches     1442     1442              
==========================================
+ Hits         4893     4902       +9     
- Misses        176      177       +1     
- Partials      131      132       +1

Impacted Files	Coverage Δ
...pt-estree/src/create-program/createWatchProgram.ts	93.12% <100%> (+0.13%)	⬆️
...ges/typescript-estree/src/create-program/shared.ts	78.57% <72.72%> (-4.77%)	⬇️