[QUIC] Don't leak QUIC session upon QuicListener disposal

[scalablecory]

We have a hang in QuicListener.Dispose() and are currently working around it by just not disposing of the session.

runtime/src/libraries/System.Net.Quic/src/System/Net/Quic/Implementations/MsQuic/MsQuicListener.cs

Lines 113 to 115 in 5c6f5b1

	// TODO this call to session dispose hangs.
	//_session.Dispose();
	_disposed = true;

[scalablecory]

Moving this to 6.0, @jkotalik does that sound okay given this will be experimental feature, and QuicListener is generally disposed at end of program in ASP.NET?

[ManickaP]

Has this been solved by: #49823 ??? Seems to me like it has. We might close this.
@scalablecory

[scalablecory]

Triage: this is probably solved due to not holding a ref to session anymore (now it is configuration, and MsQuic ref counts that itself.) -- double check code and close if it's fixed.

@ManickaP