Use TestAdapter's IFrameworkHandle for test output messages

Currently all messages are published to `SinkCoordinator` or just printed in console. Need to take these messages (possibly not all of them, but important ones) and pass to `IFrameworkHandle.SendMessage` method. This will write them in `dotnet test` output.

Start by tracing where messages are published to SinkCoordinator or printed to the console, then inspect the TestAdapter integration and IFrameworkHandle.SendMessage API. Determine which messages are important enough to forward, and verify that they appear in dotnet test output without losing existing console or sink behavior.

Written by the indexing model from the issue text.