With the introduction of Microsoft.AspNetCore.Razor.Utilities.Shared,
this assembly is no longer useful. The only types left in it were
in support telemetry, and those can easily be moved to
Microsoft.CodeAnalysis.Razor.Workspaces, which is already referenced by
most tooling projects. This will help reduce image loads in Visual
Studio.
* Remove razor-compiler.sln from root directory
* Move Razor.sln and Razor.Slim.slnf into root directory
* Put all projects from razor-compiler.sln into Razor.sln, with same solution folder layout
* Fix builds and docs
* Remove a couple of redundant files in the src\Razor folder