RESTRICT AUTOMERGE Prohibit untrusted proxys from specifying proxied attribution tags

Only trusted proxies should be allowed to specify tags. Also prevents
startOperationDryRun from editing the know attribution tags, as the dry
run should change no state.

Bug: 445917646
Test: atest AttributionTest
Flag: EXEMPT CVE_FIX
Cherrypick-From: https://googleplex-android-review.googlesource.com/q/commit:a975a8cb0b80ccf1e4b39ce4ec2502fcb794205f
Merged-In: I14ab1389384fd28009edd9cceceaacdb97fb96e5
Change-Id: I14ab1389384fd28009edd9cceceaacdb97fb96e5