Tracked in: #6157

Note: this must only be merged as part of the Qdrant 1.14 release!

Enable the new mutable ID tracker by default, and remove the now obsolete feature flag for it.

This will now use the new mutable ID tracker using custom storage in new mutable segments. It replaces the old RocksDB based mutable ID tracker.

All Submissions:

• Contributions should target the dev branch. Did you create your branch from dev?
• Have you followed the guidelines in our Contributing document?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?

New Feature Submissions:

1. Does your submission pass tests?
2. Have you formatted your code locally using cargo +nightly fmt --all command prior to submission?
3. Have you checked your code using cargo clippy --all --all-features command?