Fix fleet-scoped host vitals labels (#46953)

**Related issue:** Resolves #46869

- [X] Changes file added for user-visible changes in `changes/`,
`orbit/changes/` or `ee/fleetd-chrome/changes`.

## Testing

- [X] Added/updated automated tests
- [X] QA'd all new/changed functionality manually

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **Bug Fixes**
* Host vitals labels based on identity-provider group membership now
correctly apply to both global and team-scoped hosts, preventing
cross-team leakage.

* **Tests**
* Added and updated tests to validate IdP-group-backed vitals label
membership across global and per-team hosts.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

changes/46869-idp-team-vitals-labels

@@ -0,0 +1 @@
+- Fixed a bug where host vitals labels (e.g. IdP group/department labels) scoped to a fleet/team never got any hosts. The membership cron only looked at global labels, and team-scoped IdP labels also failed to populate due to an incorrect SQL join.