Run multiple caching schedulers

Extend the caching scheduler with some resource locking to enable the running of multiple schedulers when running the caching scheduler.

The idea involves:
* talking a lock (with timeout) of resources from compute resource manager
* refreshing the resource manager lock to prevent timeouts
* attempt to reduce resource races before adding into cache, and reduce races removing from cache
* running multiple schedulers, each with its own in-memory cache of decisions

A future idea could include:
* a shared cache between schedulers, possibly replacing the resource manager resource commit

Dependency:
this is dependent on the caching-scheduler working out OK