Refactor ClockRing structure for improved memory efficiency and functionality

- Updated the `Entry` structure to store reference bits in a separate `Vec<bool>`, enhancing cache-friendly access patterns.
- Introduced new methods for mutable access and memory management, including `get_mut_with`, `clear`, `clear_shrink`, and `approx_bytes`.
- Enhanced documentation to clarify the behavior of new methods and the layout of the `Entry` structure.
- Ensured that all public methods are marked with `#[must_use]` where applicable to promote better usage patterns.

Author: TKorr