Make new SyncNamespace refactoring work with omnisharp-roslyn

[savpek]

3.x roslyn introduced sync namespace refactoring dotnet/roslyn#14341

However it doesn't show up in omnisharp-roslyn with current version. Reason behind this is project DefaultNamespace that is null, it should be set up during project creation/updates.

Method to make it is currently internal http://source.roslyn.io/#Microsoft.CodeAnalysis.Workspaces/Workspace/Solution/Solution.cs,e596842b39b5f5f9

Heres proof of concept that after invoking that method via reflection it works as expected

Changes required for previous setup savpek@614d2e0

Roslyn issue: dotnet/roslyn#35173

[filipw]

I think the better way would be to use the API on ProjectInfo (as soon as ProjectInfo is created, not when the project is added to solution) rather than the one you pointed to, but that one is also internal http://source.roslyn.io/#Microsoft.CodeAnalysis.Workspaces/Workspace/Solution/ProjectInfo.cs,151

[savpek]

I think both are needed:

• constructor as public for case on initial startup or when new project is added to solution / workspace.
• workspace update as public to support case where user changes RootNamespace without full restart of omnisharp.