From issues identified in #5624

Plugin Features / Improvements

### Plugin Tasks
- [x] Fix bug in "install plugin" API endpoint where failure is not correctly reported - https://github.com/inventree/InvenTree/pull/5646
- [x] Automatically reload plugin registry when plugins change in another running worker - https://github.com/inventree/InvenTree/pull/5649
- [x] Automatically run migrations when a new plugin is activated - https://github.com/inventree/InvenTree/pull/5668
- [x] Improve plugin reload mechanism with mutex locking - https://github.com/inventree/InvenTree/pull/5649
- [x] Enable plugin list API to be filtered by "builtin" or "sample" status - https://github.com/inventree/InvenTree/pull/5647
- [x] Cleanup "old" plugin configs (which reference plugins which are no longer available on the system) - https://github.com/inventree/InvenTree/pull/5652
- [x] Automatically reload plugin registry when the plugin settings change - https://github.com/inventree/InvenTree/pull/5662
- [ ] Provide users with better feedback if a plugin requires features which are not enabled (like app-mixin / url-mixin / etc)
- [x] Inform users when the system has unapplied migrations (if they are not applied automatically)
- [ ] Collect more metadata for plugins which are not installed
- [ ] Check for available plugin updates periodically - e.g. https://pypi.org/project/pip-check-updates/