Geo: Make it easier to know why a resource is in the `verification_disabled` state

Proposal

Follow up for #299819 (closed) to make it easier for devs and sysadmins to know why a registry row is in verification_disabled state.

• When transitioning to verification_disabled because it is remote-stored, then set verification_failure to Verification disabled because the resource is remote-stored
• When transitioning to verification_disabled because it's not checksummed on the primary, then set verification_failure to Verification disabled because the resource is not yet checksummed on the primary
• Add/modify tests

I think it's ok to reuse verification_failure field as I don't think it will really cause confusion. Especially if the message includes "verification disabled".