Fix a bug where ICE restart with the same address would disconnect the selected connection on the callee side.

The root cause is that ports manage connections via remote addresses. If
a new generation candidate is applied on an old generation port, it may
create a new connection and replace any existing connection under the
same address, even when it is selected.

This change only blocks the replacement of selected connections so they
would still send data during ICE restart. The ICE restart should
conclude with selected connections under a new port with updated ufrag
and password. Then the connections kept here would be destroyed with the old port.

Unit test and integration test are updated accordingly.

Bug: webrtc:543082385
Change-Id: I9eb841b3f276d0c4d32d0d6d86906278e8a438a4
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/500240
Reviewed-by: Danil Chapovalov <danilchap@webrtc.org>
Commit-Queue: Tomas Gunnarsson <tommi@webrtc.org>
Reviewed-by: Tomas Gunnarsson <tommi@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#48545}