rust/bt-ascs: Implement Release operation

This change implements the client-side "Release" operation as defined
in ASCS v1.0.1, Section 5.8. This allows a client to release all
resources associated with one or more ASEs.

 - Added the `release` method to the `AudioStreamControlServiceClient`.
 - Implemented the encoding logic for the `Release` control operation.
 - Added unit tests to verify the success path and failure due to
   invalid ASE state.

Test: cargo test -p bt-ascs
Bug: b/431814103
Change-Id: I0cef17323e1d0b2c9cfd16a0d978bb086b81144e
Reviewed-on: https://bluetooth-review.googlesource.com/c/bluetooth/+/2483