[Geo] Add a worker to backfill verification state

What does this MR do?

Closes #338597 (closed)

Things left to do

• Extract BaseBatcher, MR here
• Manually test out worker
• Rebase this MR after BaseBatcher is merged, to remove those changes from this diff (Mike squashed the remaining code)
• Do some TODO code comments (the commits were left separate for visibility)
• Fix some static analysis failures (the commits were left separate for visibility)
• Check handbook guide on adding new workers
• Add more detailed logging
• Add an FF to disable this worker until all work is complete, specially #338598 (closed)?
• Add tests to VerificationStateBackfillWorker, similar to RegistryConsistencyWorker tests, to test for idempotency, job namespace
• Remove list from Geo::VerifiablesUpdateWorker#replicable_classes, use replicators instead
• Re-enqueue only when worker#execute does some work, like the RegistryConsistencyWorker
• Add tests to show it reenqueues properly
• Clean up MR

Screenshots or Screencasts (strongly suggested)

How to setup and validate locally (strongly suggested)

Does this MR meet the acceptance criteria?

Conformity

• I have included changelog trailers, or none are needed. (Does this MR need a changelog?)
• I have added/updated documentation, or it's not needed. (Is documentation required?)
• I have properly separated EE content from FOSS, or this MR is FOSS only. (Where should EE code go?)
• I have added information for database reviewers in the MR description, or it's not needed. (Does this MR have database related changes?)
• I have self-reviewed this MR per code review guidelines.
• This MR does not harm performance, or I have asked a reviewer to help assess the performance impact. (Merge request performance guidelines)
• I have followed the style guides.
• This change is backwards compatible across updates, or this does not apply.

Availability and Testing

• I have added/updated tests following the Testing Guide, or it's not needed. (Consider all test levels. See the Test Planning Process.)
• I have tested this MR in all supported browsers, or it's not needed.
• I have informed the Infrastructure department of a default or new setting change per definition of done, or it's not needed.

Security

Does this MR contain changes to processing or storing of credentials or tokens, authorization and authentication methods or other items described in the security review guidelines? If not, then delete this Security section.

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team