Disallow deleting accessories that have active checkouts

[marcusmoore]

This PR prevents deleting accessories that are checked out to assets or locations (we already prevent deleting accessories checked out to users). We already disable the button on the accessory show page but did not on the index page.

The API and UI controllers now take into account all checkouts to the accessory and the index has been updated to disable the button if the item has checkouts:

[what-the-diff]

PR Summary

• Improved Deletion Process in Accessories Controllers:
  The code for removing accessories has been updated to consider the number of associated 'checkouts' before processing. This means that an accessory can only be deleted if it isn't tied to any checkouts, ensuring consistency.

• Enhancements in Accessory Creation Process:
  There are two new ways to create accessories tied to specific 'assets' and 'locations'. These methods simplify and streamline the creation process.

• Reliability Improvements in Deletion Tests:
  Tests regarding the deletion of accessories have been improved to include scenarios where accessories are tied to other 'users', 'assets', and 'locations'. This ensures that all potential situations are considered during testing, thereby improving the reliability of the process.