Consider use of ahash and parking_lot crates

At IETF 124 meeting, an individual recommended that we adopt the following crates:
- ahash - faster and more secure HashMap than Rusts standard HashMap, more info here: https://docs.rs/ahash/latest/ahash/
- parking_lot - faster and more flexible than built-in Rust Mutex, this effort includes a review of Mutex use and replace with RWLocks appropriately: more info here: https://docs.rs/parking_lot/latest/parking_lot/

The issue names no files, tests, or entry points. Start by auditing the repository's current HashMap and Mutex usage, then review the ahash and parking_lot documentation linked in the issue. Done means deciding whether to adopt either crate, identifying appropriate Mutex-to-RwLock changes, and documenting or implementing the resulting scope.

Written by the indexing model from the issue text.