Use format_inspector from oslo

This removes the in-tree format_inspector and makes us use the one in
oslo.utils. Minor changes are required around the behavior of the
safety_check() (raising instead of returning). This also allows images
detected as 'gpt' but registered as 'raw', since that's how everything
currently works. Hopefully later we can start registering in glance as
gpt, and rejecting boots from raw images.

Change-Id: I5b89e17438157690495961c306861a06532c8b4e
Depends-On: https://review.opendev.org/c/openstack/tempest/+/927146

requirements.txt

@@ -38,7 +38,7 @@ oslo.limit>=1.5.0 # Apache-2.0
 oslo.reports>=1.18.0 # Apache-2.0
 oslo.serialization>=4.2.0 # Apache-2.0
 oslo.upgradecheck>=1.3.0
-oslo.utils>=4.12.1 # Apache-2.0
+oslo.utils>=7.3.0 # Apache-2.0
 oslo.db>=10.0.0 # Apache-2.0
 oslo.rootwrap>=5.15.0 # Apache-2.0
 oslo.messaging>=14.1.0 # Apache-2.0