Move classification helper code so it will be usable by the new async find refs service.

Remove unused FindAllReferences method.

Navigable items can state if they are relate to implicitly declared items or not.  We want this as we will not display unreference implicitly declared nav items.

* Enable building and testing on machines with only Dev15 Preview 3 installed

1. Auto-detect the VS common tools path
2. Convert analyzer samples to import Roslyn targets
3. Ensure dependencies are copied to the output directory
4. Workaround: Use local Microsoft.Net.Compilers.props until we move to a compiler toolset with https://github.com/dotnet/roslyn/commit/05c12ebfcdd08a02dbceded5327a8da7a7df23be
5. Replace references to Microsoft.VisualStudio.ComponentModelHost.dll (VisualStudioReferenceAssemblyVersion) with a nuget reference to RoslynDependencies.Microsoft.VisualStudio.ComponentModelHost
6. Add nuget references to Roslyn.Microsoft.Build, Roslyn.Microsoft.VisualStudio.ExtensionManager, RoslynDependencies.Microsoft.VisualStudio.Diagnostics.PerformanceProvider and RoslynDependencies.Microsoft.VisualStudio.CodeAnalysis.Sdk.UI.

* Remove workaround now that new NuGet packages have been uploaded to nuget.org

* Remove preprocessor directive MSBUILD12 and its references

Merge dev15-preview-4 into master

Remove quick info parameters that were never used.

Navigable items can state if they are relate to implicitly declared items or not.  We want this as we will not display unreference implicitly declared nav items.

Currently, if you implement an interface with a tuple type as a
substituted type argument that will be accurately represented in source,
but the names will be lost when emitted to metadata.

This PR implements roundtripping for tuples as generic type arguments to
interface implementations in metadata. This is done by adding support
for emitting attributes on interface implementations to Emit. We now
emit the same attribute on interface implementations that we would
on other areas where types may contain nested tuples. Completes the
interface implementation work referenced in #12347.

Enable Completion filtering and highlighting by default

Merge telemetry sources into existing projects

Now that the telemetry API is consumable from OSS and the code is there, no
need to have a dedicated binary + vsix for it.

Share refactoring code between C# and VB.

Merge dev15-preview-4 into master

Do not go back to the symbol to determine what text we will insert for a completion item.

Support doc comments for symbols declared off an anonymous type.

Fixes #12530