Fix facility n+1

[AnkurPrabhu]

Proposed Changes

• Brief of changes made. using prefetch related for both the fields (PatientRegistration and Bed)

Associated Issue

fixes: #1920

Architecture changes

• Remove this section if not used

Merge Checklist

• [x] Tests added/fixed
• [ ] Update docs in /docs
• [x] Linting Complete
• [x] Any other necessary step

Only PR's with test cases included and passing lint and test pipelines will be reviewed

@coronasafe/care-backend-maintainers @coronasafe/care-backend-admins

[AnkurPrabhu]

@sainak have resolved your comments pls take a look

[vigneshhari]

Closing this because we are considering an approach with redis based caching with existing design.