Making `MutexGuard`, `RwLockReadGuard` & `RwLockWriteGuard` more generic

Currently, the locks guards are defined like this:

pub struct MutexGuard<'a, T: ?Sized + 'a> {
    lock: &'a Mutex<T>,
    poison: poison::Guard,
}

But there are a lot of instances where taking a reference to the lock is not as versatile as it could be, so perhaps a redefinition of the locks to something like this makes more sense.

pub struct OwnedMutexGuard<M: Deref<Target = Mutex<T>>, T: ?Sized> {
    lock: M,
    poison: poison::Guard,
}

pub type MutexGuard<'a, T> = OwnedMutexGuard<&'a Mutex<T>, T>

No repository files or tests are named. Start by locating the current MutexGuard, RwLockReadGuard, and RwLockWriteGuard definitions and their construction and usage sites; determine whether generic owned guards and reference-based aliases can be designed consistently, then document the resolved API and compatibility behavior.