More test refactorings

Split the public API files

Express command visibility in vsct...

This will allow VS to figure out when to display the "Reset Interactive from Project" command without having to load the Interactive assemblies (execute code).

Move portable sources from TestUtils to TestUtils2

Fix xml doc gen with escaped identifiers

This change splits the files for public API tracking into:

- PublicApi.Shipped.txt: APIs shipped in the previous version of Roslyn
- PublicApi.Unshipped.txt: APIs shipped in the next version of Roslyn

This makes it very easy for us to tell at a glance the API change which is being
carried in a given branch of Roslyn.

Don't bother creating taggers when there are no diagnostics to display.

Enable InteractiveConsole.BreakLine

Update Xunit to build 3109, which has shadow copy fix

...when the Interactive window is open.

Fixes #4437

More Jenkins updates

When assigning decimal/datetime constant fields, the FieldAccess sho…

Jenkins patch

Clean up CompilerTestUtilities2 - remove non-portable and unused code

[PortablePDB] Implement GetOffset, GetRanges, FindClosestLine

Remove test workaround for a fixed DiaSymReader bug 1068894

When assigning decimal/datetime constant filelds, the FieldAccess should not be considered a constant.

Fixes #4383

Produce an error when __makeref is used and TypedReference type is no…

Ensures that history always contains what user has typed

Remove SCC bindings

Canonicalize all interactive window commands