- Change most tests to use dynamic ports, rather than a fixed port obtained from GetNextPort().
- Add several new cases to `AddressRegistrationTests` and `ServerAddressFacts`.
- Remove project `test\Microsoft.AspNetCore.Server.Kestrel.TestCommon`. It's not longer needed, since only `AddressRegistrationTests` uses `GetNextPort()`.
- Even when safe handles are disposed explicitly, ReleaseHandle is sometimes
called on another thread which breaks uv_close.
- Ensure we close the UvAsyncHandle the uv loop so that the second call
to uv_run always completes without a timeout/Thread.Abort.
- Re-enable some tests. Add skip conditions for those that aren't passing.