Refactoring of Windows PDB Custom Debug Information decoder

Make code action application more async.

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Fix up references to MS.VS.D.Engine and MS.VS.D.Metadata...

Several of our EE binaries needed to be signed with different certificates than the standard Microsoft one.  Functionality was added to specify the certificate for the binary in question and all remaining references to the AuthenticodeCertificateName property were removed.

We need to consume the VSSDK nugets for these assemblies in order to
build/run on a machine without VS 2015.

Preserve trailing trivia in 'Replace Property with Methods'

Fix remaining fast up to date check issues

Merge dev15-preview-4 into master

If you have a content file in a shared project, the project system
gets confused in the head project where the output will go, causing the
project to always rebuild. This is tracked as internal bug 239691, and
this works around it for now.

- Use the MSBuild standard Content support instead of reinventing it
- Avoid having a duplicate assembly name in the solution
- Ensure that a placeholder binary is made to placate the fast up-to-
  date check

This works around #12458. The warnings are annoying and also break
the project system in slightly bad ways.

Implement "target type preselection" redux

Fix stack overflow in VB F1 Help visitor.

Port insertion fixes into dev15-preview-4

Adding back 'Microsoft.VisualStudio.Shell.Interop.SVsLog` interop type.

Adding back 'Microsoft.VisualStudio.Shell.Interop.SVsLog` interop type.

This adds back `src/Compilers/Core/Portable/Interop/IVsSQM.cs` file and re-adds it to the `src/VisualStudio/Core/Def/ServicesVisualStudio.csproj` project because there is a some VS code with IVT that currently depends on the interop type existing.

Bump the pre-release version to beta5

Don't mention 'switch' so lightbulb text can apply equally to VB and C#

Fixes #12235

Add a way to get syntax trees synchronously for features that need them.