[dotnet-watch] Include AddExplicitInterfaceImplementation capability

[tmat]

We have two code paths that get capabilities from the runtime: the debugger reads them via VIL evaluation and the Hot Reload agent reads them here .

The latter is missing AddExplicitInterfaceImplementation capability, which is an implicit capability that is not returned by the runtime but is supported by .NET runtime (and not by .NET Framework).

Fixes https://devdiv.visualstudio.com/DevDiv/_workitems/edit/2655394

Follow ups:

• Update source package version in Project System
• Delete https://github.com/dotnet/roslyn/blob/ac3431e351642a7ab47d1a8d82a3964efe57bdc8/src/Features/ExternalAccess/HotReload/Api/HotReloadService.cs#L154 as it's no longer needed
• Consider eliminating the VIL evaluation code path to avoid duplication

[tmat]

@DustinCampbell ptal

[DustinCampbell]

Looks good

[tmat]

/ba-g known issues