Refactor DispatcherProvider to improve testing coroutine timing (DEV) #2190

* Adjust DispatcherProvider interface to return type `CoroutineContext`.
This is a preamble to fix a few coroutine tests that require time advancement.
We need to be able to pass the TestCoroutineScope's context to classes under test.
This can now be done using CoroutineContext.asDispatcherProvider().

* Fix compile error in test

Co-authored-by: Ralf Gehrer <ralfgehrer@users.noreply.github.com>
Co-authored-by: ralfgehrer <mail@ralfgehrer.com>