Refactorings to be added in C#

[arunchndr]

The C# extension currently doesn't support (or I've just been unable to trigger) several C# refactorings / quick actions, including the following:

Convert to Namespace
Convert to program 'main'
Convert to top-level statements
Convert concatenation to interpolated string
Convert between 'foreach' and LINQ query
Move static members
Name tuple element
Replace conditional with statements
Replace doc comment text with tag