Adds PublicApiAnalyzers to public projects

[josh-degraw]

RE: #204
Notes:

• Moved PackageReference for PublicApiAnalyzers into src directory so it only shows for public projects.
• Turned off warning for RS0017 (Remove deleted types and members from the declared API).
  • Since some properties (specifically SentryOptions.MaxRequestBodySize) are only declared for certain platforms, the warning will show up if it's in the .txt file, and RS0016 (Add public types and members to the declared API) will show up if it's not, and since TreatWarningsAsErrors is enabled, it breaks the build either way.
  • I opted to suppress the first so that things will always be included, but that's a potential bug in the analyzer itself that should be noted.

[codecov-io]

Codecov Report

Merging #234 into master will increase coverage by 0.09%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #234      +/-   ##
==========================================
+ Coverage   88.84%   88.94%   +0.09%     
==========================================
  Files          81       81              
  Lines        2035     2035              
==========================================
+ Hits         1808     1810       +2     
+ Misses        227      225       -2

Impacted Files	Coverage Δ
src/Sentry/Internal/BackgroundWorker.cs	95.9% <0%> (+1.63%)	⬆️

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[bruno-garcia]

Thanks again for contributing!
Looks good to me, just one comment about the strategy to ignore warnings.

[bruno-garcia]

! Thanks Josh!