Fixes #34483, #36112

Change dotnet_diagnostic.*.severity settings to match code style

- Microsoft.DotNet.Arcade.Sdk - 1.0.0-beta.19323.4

Support nullable variance in interface and partial method implementation.

Closes #35227.

* Update dependencies from https://github.com/dotnet/arcade build 20190620.1

- Microsoft.DotNet.Arcade.Sdk - 1.0.0-beta.19320.1

* Bring changes from https://github.com/dotnet/arcade/pull/3076

* Update dependencies from https://github.com/dotnet/arcade build 20190621.75

- Microsoft.DotNet.Arcade.Sdk - 1.0.0-beta.19321.75

* Update dependencies from https://github.com/dotnet/arcade build 20190622.2

- Microsoft.DotNet.Arcade.Sdk - 1.0.0-beta.19322.2

Update to Roslyn.Diagnostics.Analyzers 2.9.3

Update Building, Debugging, and Testing on Windows.md

* added NFW to get some data on incremental parsing bug where source size and tree size is different

* more comments

Use IFeatureServiceFactory to disable async completion

Wire NullableWalker snapshotting to the public SpeculativeSemanticModel apis

Add some nullability tests for Generate Type and fix one bug

Closes https://github.com/dotnet/roslyn/issues/30316

The code style settings we already had in a .editorconfig file supplied
a set of terms to set different diagnostic severities. The terms don't
match the underlying compiler enum, but we will adopt them for
setting compiler diagnostic settings as well to keep the values
consistent inside a .editorconfig file.

Fixes https://github.com/dotnet/roslyn/issues/35690

Also add extension methods to help with nullability

* dotnet/master: (85 commits)
  Don't complete statement when typing semicolon inside comments in an argument list (#36521)
  Set focus to editor before finding text
  Add a bunch of nullability support to some code generation helpers
  Add 'annotations' and 'warnings' support to nullable directive (#36464)
  Fixed IDE services touching `notnull` constraint (#36508)
  Update compiler toolset to arcade version (#36549)
  Fix for 923157
  Do not include value types in NullableAttribute byte[] (#36519)
  Fix a deadlock in InvokeOnUIThread
  Apply a hang mitigating timeout to UI thread operations
  Move to a different lowering from for nullable value types to work around a bug in TransformCompoundAssignmentLHS. Addressed PR feedback.
  Fix stack overflow in requesting syntax directives (#36347)
  crash on ClassifyUpdate for EventFields (#35962)
  fixing bad merge with refactoring that was checked in later
  added basic completion statement telemetry
  Remove duplication in AbstractSymbolCompletionProvider.CreateItems
  Disable move type when the options service isn't present (#36334)
  Fix crash where type inference doing method inference needs to drop nullability
  Revert "Use IVsSolution to look up IVsHierarchy by project GUID (#35746)"
  Fix parsing bug in invalid using statements (#36428)
  ...

Closes #33807

Set focus to editor before finding text

Add a bunch of nullability support to some code generation helpers

* Fix for typing semicolon inside comments in an argument list

* Change to previously existing method

* Fix

Closes #36401

Merge release/dev16.2-preview3 to master

* Add optional [warnings | annotations] keyword to nullable directive

* pragma warning <setting> nullable -> nullable <setting> warnings

* Implement /nowarn:nullable