DatabaseCache - Support batching in set_many

### Code of Conduct

- [x] I agree to follow Django's Code of Conduct

### Feature Description

DatabaseCache currently supports `set_many`, by iterating each item one by one and saving. This can be a slow loop when saving many items, and would benefit from bulk creation of records, overriding the default.

### Problem

This will save time when saving multiple cache records. No other tangible benefit comes to mind.

### Request or proposal

proposal

### Additional Details

I'm happy to drop a pull request for this change, but this would be my first for this project so may make mistakes.

### Implementation Suggestions

I was thinking about just overriding the existing `set_cache` method on the DatabaseCache cache backend, bulk creating records instead of one at a time.

Start by locating the DatabaseCache cache backend and reading its set_many and set_cache methods to understand the current per-item save behavior. Check the cache backend tests and existing bulk-operation conventions before changing the persistence path. Done means set_many stores multiple records through a bulk operation while preserving the existing cache behavior and passing the relevant tests.

Written by the indexing model from the issue text.