Simplify distributed locking extension system

[Turnerj]

Simplifies the distributed locking extension system, dropping the ICacheRefreshCallSiteWrapperExtension interface for a more direct IDistributedLockExtension with then a major overhaul to the RedisLockExtension.

The main benefits of this is that it avoids the responsibility of the cache factory from getting passed into the extension and instead just allows the extension to control the distributed lock behaviour.

It may reduce allocations from closures but more importantly, actually just makes the code easier to work with and the extension system a bit nicer. It being easier to work with allows more opportunity for flexibility around this code including logging, metrics, other traceability and even just other method signatures.