make all integration tests retryable. nullability clean up

[david-driscoll]

No description provided.

[codecov]

Codecov Report

Merging #460 (a669963) into master (acb618b) will decrease coverage by 4.36%.
The diff coverage is 79.28%.

@@            Coverage Diff             @@
##           master     #460      +/-   ##
==========================================
- Coverage   71.26%   66.89%   -4.37%     
==========================================
  Files         251      252       +1     
  Lines       11920    11900      -20     
  Branches      810      812       +2     
==========================================
- Hits         8495     7961     -534     
- Misses       3425     3939     +514     

Impacted Files	Coverage Δ
src/Client/LanguageClient.cs	97.22% <ø> (ø)
src/Client/LanguageClientOptionsExtensions.cs	13.54% <ø> (-29.17%)	⬇️
...lient/LanguageClientServiceCollectionExtensions.cs	96.96% <ø> (ø)
src/Client/LspClientReceiver.cs	75.00% <ø> (ø)
src/Dap.Server/ProgressObserver.cs	16.00% <ø> (ø)
src/Dap.Testing/DebugAdapterProtocolTestBase.cs	100.00% <ø> (ø)
src/JsonRpc.Generators/ActionContextExtensions.cs	100.00% <ø> (ø)
...JsonRpc.Generators/AutoImplementParamsGenerator.cs	92.20% <ø> (ø)
src/JsonRpc.Generators/Cache/CacheContainer.cs	100.00% <ø> (ø)
src/JsonRpc.Generators/Cache/CacheKeyHasher.cs	80.45% <ø> (ø)
... and 114 more

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