Locker v2

[corhere]

Breaking changes:

• The minimum Go version is go1.19
• The result parameter to (*Locker).Unlock() has been dropped. Instead the application will crash with the same fatal run-time error as calling (sync.Mutex).Unlock() on an unlocked mutex.
• ErrNoSuchLock has been removed.
• New() has been removed. The zero value is valid.

Modernize the codebase by taking advantage of Go 1.19 atomics. Add an RWLocker for read-write locks. Add sync.Locker interface adapters for Locker and RWLocker.