cratesland/mea

AI Summary: Implement six variants of `MappedMutexGuard` for Mea's `Mutex` and `RwLock` types, handling both owned and non-owned scenarios, and supporting lock, read lock, and write lock operations. This involves adapting the existing `Mutex` and `RwLock` implementations to allow for mapping the locked data using a closure, similar to Tokio's and std's `MappedMutexGuard`.

AI Summary: Implement a rendezvous (zero-buffer) version of the existing mpsc channel in the Mea library. This requires a different underlying implementation than the current unbounded channel, but the public API can remain largely consistent. The new implementation should reside in a separate module for maintainability.