Add add-using option to run out of process, and update tests to run both codepaths. (Note: add-using OOP not actually implemented yet).

Fix Extract Method operations within an event accessor

Fix IDE0009 false positive on expressions qualified with 'base.'

	Remove direct access to the IPackageInstaller service from add-usings search engine

Switch to using a string instead of a full diagnostic.

Add missing null check to WorkspaceMetadataFileReferenceResolver.Equals

Flaky test in Roslyn.VisualStudio.IntegrationTests.VisualBasic.BasicExpressionEvaluator.StateMachineTypeParameters (#19966)

Fix VB IUsingStatement.Declaration to not have null syntax.

Closes #19136

Smarter resource management in MemoryMappedInfo

Pass a project when creating an invisible editor

Fix code generation for duplicate events

Fixes #17474

Ensure that IOperations nodes within a C# local function are part of …

Change data flow analysis to pass a location for error reporting if a branch is compiler generated
or if it is null (which is effectively compiler generated).

Fixes #18813

Fix race condition in EnC implementation

Fixes #18792

Handle the case where a project doesn't have an output directory set.