Clear completion pattern matcher caches on solution close

get ParseOptions from ProjectState rather than calculate one itself

Skip deriving IArgument if there's error in parameter type

Cast the correct object to IVsBrowseObjectContext

According to [Finding CPS in a VS project](https://github.com/Microsoft/VSProjectSystem/blob/master/doc/automation/finding_CPS_in_a_VS_project.md)
we should cast an `EnvDTE.Project` instance directly to `IVsBrowseObjectContext`. Currently we take the
object returned by `EnvDTE.Project.Object` and cast that, but this seems to only be valid for VC projects.

Fix a typo in the Build NuGet script

Add build status for the dev15.6 branch

Don't crash and send an NFW if debugger contenttype does not match

Updating VSIXExpInstaller to 0.4.0-beta

Updating BuildAndTest.proj to explicitly uninstall extensions from a previous build before installing new ones.

Capture exception info for integration test failures

Will capture the exception stack trace in addition to the screen shot
when a first chance exception occurs running our integration tests.

Support adding PackageReferences to CPS projects

Add support for inspecting Solution Explorer items

We need this version to avoid conflicts with other assemblies that
reference a different version of the System.Composition.* assemblies.

We're on a background thread already, so we can just block on the calls to `AddAsync` and `RemoveAsync`.

Add APIs to allow integration tests to add PackageReferences to CPS projects.

Add basic support for inspecting Solution Explorer items.

changed logger to log errors from all analyzers not just first analyzer

We've received watsons that indicate that a VB file is being set as the
"context buffer" for C# debugger intellisense. It appears that this
would only happen if the debuggered called us with a buffer of the wrong
content type. Add an assertion that the content type is correct.

Related to
https://devdiv.visualstudio.com/DevDiv/_workitems?id=397711&_a=edit&triage=true

made diagnostic engine to verify span given to diagnostic from analyz…

Optimize fast path for "Use 'var'" code style

Update IDE Test Plan with 15.3 features

Properly push events to the OOP side so that we know when things like solution-closing happens.
Fixes #19768