… tests for failing case (elastic#201517)

## Summary

Currently, the partitionPatchRequest in
x-pack/plugins/cases/server/client/cases/bulk_update.ts will not check a
case properly if a case is being re-opened, instead of an else if in the
loop comparing cases to cases in the request, the status logic should be
outside of this set of if statements. If a case is being re-opened, the
final else is never run, and casesToAuthorize is 0. This results in
ensureAuthorized being called with an empty array of entities, and so
the check always succeeds. To fix this, reopenedCases is still populated
in the same loop, just not when casesToAuthorize logic is running as
well. Also adds some missing tests for this and the create comment
permission as requested in
elastic#194898.

### Checklist

- [x] [Unit or functional
tests](https://www.elastic.co/guide/en/kibana/master/development-tests.html)
were updated or added to match the most common scenarios

This pr implements a new cases assignee sub-feature, allowing users to
control a role's ability to change the assignee of a case. With the
permission enabled, they can assign any user to any case, with it
disabled, the assignees component is hidden.

Read only + enabled:

![image](https://github.com/user-attachments/assets/ba421784-d976-4ae9-a399-e404c26b3842)

All + assign disabled:

![image](https://github.com/user-attachments/assets/d835b6f9-5a14-4ae0-abed-b3c3252c2692)

- [ ]
[Documentation](https://www.elastic.co/guide/en/kibana/master/development-documentation.html)
was added for features that require explanation or tutorials
- [x] [Unit or functional
tests](https://www.elastic.co/guide/en/kibana/master/development-tests.html)
were updated or added to match the most common scenarios

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Co-authored-by: Elastic Machine <[email protected]>