Suppress harmless denials for file creation in cgroupfs.

The kernel generates file creation audits when O_CREAT is passed even
if the file already exists - which it always does in the cgroup cases.

We add neverallow rules to prevent mistakenly allowing unnecessary
create access. We also suppress these denials, which just add noise to
the log, for the more common culprits.

Bug: 72643420
Bug: 74182216

Test: Ran build_policies.sh and checked failures were unrelated.
Test: Device still boots, denials gone.
Change-Id: I034b41ca70da1e73b81fe90090e656f4a3b542dc