Remove static Coverage object

[MarcoRossignoli]

contributes to #387
closes #364
replace #366

• Removed static InstrumentationTask.Coverage and used [Output] msbuild parameter

Instrumenter state is serialized using IInstrumentStateSerializer for now implemented with JsonSerializer

• Organized coverlet internals in two main interface IInstrumenter and ICoverageCalculator
• Organized cs files under project folder Instrumentation and Coverage
• Cleanup msbuild Task parameter using auto prop

/cc @tonerdo @petli @sharwell

[MarcoRossignoli]

for simplicity I used Json serializer.

[MarcoRossignoli]

we need custom converter because Json serializer does not support serialization of complex dictionary key

[codecov]

Codecov Report

Merging #393 into master will decrease coverage by 0.69%.
The diff coverage is 95.33%.

@@            Coverage Diff            @@
##           master     #393     +/-   ##
=========================================
- Coverage   86.96%   86.26%   -0.7%     
=========================================
  Files          16       17      +1     
  Lines        2178     2220     +42     
=========================================
+ Hits         1894     1915     +21     
- Misses        284      305     +21

[MarcoRossignoli]

@tonerdo fixed conflicts...the change touch a lot of file if you can review this before others we avoid too much conflicts...I think(hope) this is the only "huge" update of checklist.

[tonerdo]

@MarcoRossignoli this is a good start. I'm a bit skeptical about the drastic changes and I wonder if things could be simpler. The most important things that need to be serialized in the Coverage class is identifier, _module, _mergeWith, _useSourceLink, and _results (maybe _logger). I wonder if we can just extract those into their own class, serialize those and add a sort of "builder" method on Coverage that takes that class as a parameter.

Also, it's best not to do major style refactorings for important features so it doesn't get so large

[MarcoRossignoli]

Replaced by #409 keep this PR as useful notes.