docs(MAINTAINERS): Cover pre-release generation (#9235)

closes: #9234

## Description

Update MAINTAINERS.md and scripts/get-released-tags to be more
descriptive about expected use.

### Security Considerations

n/a

### Scaling Considerations

n/a

### Documentation Considerations

Included in code changes.

### Testing Considerations

None.

### Upgrade Considerations

Non-technical processes such as internal handoff are not included and
are expected to remain in upgrade runbooks.