rgw/policy: Allow logging policy evaluation

rgw/policy: Allow logging policy evaluation

When the `rgw_copious_policy_logging` option is set to true, a
detailed trace of policy evaluation is logged.

Assisted-by: Claude Opus 4.6 <noreply@anthropic.com>
(I wanted to see how it performed on rebase conflict resolution.)
Assisted-by: Claude Fable 5 <noreply@anthropic.com>
(I figured I should have it look at the policy evaluation code for
bugs while it's included, and it found a few mistakes in output.)
Signed-off-by: Adam C. Emerson <aemerson@redhat.com>