test: add simple virtio proxy networking tests and move mirrored tests to their own class (#13838)

* test: add simple virtio proxy networking tests

* move mirrored tests to their own class

* fix failing mirrored variation

* use different port for HostUdpBindDoesNotPreventGuestTcpBind

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Co-authored-by: Ben Hillis <benhill@ntdev.microsoft.com>

Author: benhillis