rgw/sts: correcting the evaluation of session policies

rgw/sts: correcting the evaluation of session policies
passed in with AssumeRoleWithWebIdentity.

Session Policies are used to restrict the permissions
granted by identity-based (Role's permission policy
and resource-policy (bucket policy) in some cases.

Fixes: https://tracker.ceph.com/issues/51019
Signed-off-by: Pritha Srivastava <prsrivas@redhat.com>
(cherry picked from commit bd611d451aaaba65c6c1b7a91ec4486142c90522)

Conflicts:
	src/rgw/rgw_op.cc

Cherry-pick notes:
- conflict due to rgw::sal::RGWObject renaming to rgw::sal::Object after Pacific