Add missing operators in tokenizer, handle end-of-comment completion better

[MikhailArkhipov]

Fixes #1096
Fixes #1123

• Add => and <= to operators in tokenizer + test
• Specifically check if completion position is at very end of the comment token + test

[DonJayamanne]

Please use the standard PR template

[DonJayamanne]

if (token.end === offset && token.type === TokenType.Comment) {

[codecov]

Codecov Report

Merging #1129 into master will increase coverage by 0.09%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #1129      +/-   ##
==========================================
+ Coverage   71.79%   71.89%   +0.09%     
==========================================
  Files         260      260              
  Lines       11892    11898       +6     
  Branches     2107     2112       +5     
==========================================
+ Hits         8538     8554      +16     
+ Misses       3225     3220       -5     
+ Partials      129      124       -5

Impacted Files	Coverage Δ
src/client/extension.ts	97.22% <100%> (-0.04%)	⬇️
src/client/providers/completionSource.ts	93.22% <100%> (ø)	⬆️
src/client/providers/providerUtilities.ts	100% <100%> (ø)	⬆️
src/client/language/tokenizer.ts	96.32% <100%> (+0.03%)	⬆️
...rc/client/debugger/PythonProcessCallbackHandler.ts	52.3% <0%> (+0.65%)	⬆️
src/client/debugger/PythonProcess.ts	48.75% <0%> (+3.33%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update f19c0d0...01b4bea. Read the comment docs.

[DonJayamanne]

@MikhailArkhipov
You failed to add the news entry files. I'll create a separate issue for that.
I guess I should have been specific about this, I was hoping you'd check those out when using the standard PR template.