Adds API mixin for "bulk delete"

[SchrodingersGat]

• Introduces a BulkDelete API mixin class
• Allows deletion of multiple items against a single API request
• Advantages are atomicity and speed
• Disadvantages are there are fewer things to debug

Ref: #3143 (comment)

TODO

Refactor (and add unit testing) for the following models which currently implement the inventreeMultiDelete function

• Stock Item Test Result
• Attachments
• BOM items
• Supplier Parts
• Manufacturer parts
• Manufacturer part parameter
• Stock items
• Delete outdated inventreeMultiDelete function (JS)

[matmair]

Suggestion (nitpik): I think it would be easier to understand if we just had a single test for multi-delete in InvenTree/InvenTree with one model instead of testing with each view that inherits the mixin.