Revert "Add hidden API to register/unregister QUIC connection cl..."

Revert submission 3538339

Reason for revert: Likely culprit for b/406432012 - verifying through ABTD before revert submission. This is part of the standard investigation process, and does not mean your CL will be reverted.

Reverted changes: /q/submissionid:3538339

Change-Id: I61b02f2b1b667e9a41b677f8062e8e96aac09f6e
10 files changed