rgw/auth: handle HTTP OPTIONS with v4 auth

rgw/auth: handle HTTP OPTIONS with v4 auth

This adds code to properly verify the signature
for HTTP OPTIONS calls that is preflight CORS
requests passing the expected method in the
access-control-request-method header.

Fixes: https://tracker.ceph.com/issues/62033
Signed-off-by: Tobias Urdin <tobias.urdin@binero.com>
(cherry picked from commit 814cae52baf04d9c3f0f3bd04b8e2daf16eb3874)