Allow IPv6 addresses to be canonical

In #17604 (moved), we allowed IPv6 connections to set is_canonical_to_peer. But we did not let them set is_canonical.

So channel_tls_process_netinfo_cell() handles IPv6 addresses, but connection_or_check_canonicity() does not.

This inconsistency could be one cause of the logging issues in #24841 (moved).

We should allow IPv6 connections to be canonical. We should also do some cleanup of the related connection address logging in #33898 (moved).

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