fix(typescript-estree): only call watch callback on new files

[uniqueiniquity]

Addressing #243

Currently we are creating a new ts.Program for every subsequent file linted after the first in a given run with the project object given.

Here we cut down the number of times this happens by ensuring we only tell the TS API that a file has changed when we lint a file for a second time (thereby implying a --fix mode or "watch" mode).

[codecov]

Codecov Report

Merging #367 into master will decrease coverage by 0.03%.
The diff coverage is 100%.

@@            Coverage Diff            @@
##           master    #367      +/-   ##
=========================================
- Coverage   97.24%   97.2%   -0.04%     
=========================================
  Files          67      67              
  Lines        2357    2360       +3     
  Branches      336     337       +1     
=========================================
+ Hits         2292    2294       +2     
  Misses         44      44              
- Partials       21      22       +1

Impacted Files	Coverage Δ
packages/typescript-estree/src/tsconfig-parser.ts	91.8% <100%> (-1.31%)	⬇️