For #29400.
Added test fails without the change to retry upon deadlocks.
How to reproduce in UI:
1. Create 10 policies on a team.
2. Refetch host to have results for the policies.
3. Add (could be the same) or update the installer associated to the 10
policies in "Manage automations" > "Software".
4. Hit `Save`.
- [X] Changes file added for user-visible changes in `changes/`,
`orbit/changes/` or `ee/fleetd-chrome/changes`.
See [Changes
files](https://github.com/fleetdm/fleet/blob/main/docs/Contributing/guides/committing-changes.md#changes-files)
for more information.
- [X] Added/updated automated tests
- [X] Manual QA for all new/changed functionality
<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit
* **Bug Fixes**
* Improved the reliability of policy updates on the "Manage automations"
page by automatically retrying requests in case of deadlock errors.
* **Tests**
* Added a test to verify that concurrent policy updates handle deadlocks
correctly and complete without errors.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
Lucas Manuel Rodriguez
dc5c396f35