feat(framework-core): return review number and variable renaming

[TomKristie]

Renamed user input for text file content of 'diffs' rawChanges to diffContents.
Renamed variable name references to this user diff file contents as well, i.e. testRawContents -> testDiffContents
Renamed RawContents object to FileDiffContents

Changed return type from void to returning the review number, or null if there was no exception but a review was not created. More succinctly, the return type is number and null. null was chosen since it clearly indicates the "lack-of-existance" of a review.

Moved the logging of successful review into the callee since the reviewPullRequest caller method does not always return a number. Having the successful log directly after the corresponding async call was made rather than in the caller allows for better logging control. Now the callee handles the logging of when there are no reviews to be made and when there is a successful review.

Towards #105

[codecov]

Codecov Report

Merging #117 into comment-pr will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@              Coverage Diff               @@
##           comment-pr     #117      +/-   ##
==============================================
+ Coverage       91.87%   91.89%   +0.01%     
==============================================
  Files              25       25              
  Lines            2290     2295       +5     
  Branches          161      164       +3     
==============================================
+ Hits             2104     2109       +5     
  Misses            185      185              
  Partials            1        1              

Impacted Files	Coverage Δ
src/github-handler/comment-handler/index.ts	100.00% <100.00%> (ø)
...ler/make-review-handler/upload-comments-handler.ts	99.20% <100.00%> (+0.02%)	⬆️
...handler/raw-patch-handler/hunk-to-patch-handler.ts	100.00% <100.00%> (ø)
...andler/raw-patch-handler/in-scope-hunks-handler.ts	100.00% <100.00%> (ø)
...handler/comment-handler/raw-patch-handler/index.ts	100.00% <100.00%> (ø)
...ment-handler/raw-patch-handler/raw-hunk-handler.ts	100.00% <100.00%> (ø)
src/index.ts	99.54% <100.00%> (-0.01%)	⬇️
src/types/index.ts	100.00% <100.00%> (ø)

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