[edge] Unify cache factory implementations

[butonic]

We currently have multiple cache factory implementations sprinkled all over the place:

• ocis/ocis-pkg/store
• reva/pkg/storage/cache
• ttlcache used in various packages (eosfs, owncloudsql, ocs, ocdav)

This creates a lot of friction when adding or trying to fix an implementation

We want to unify them by creating a new reva/pkg/store package that has a store.Create() function currently found in ocis-pkg/store as well as reva/pkg/storage/cache and contains subpackages for

• etcd (moved over from ocis-pkg/store/etcd)
• ocmem (moved over from ocis-pkg/store/memory)
• redis (a - yet to fork and fix - version of go micros redis implementation with a proper List() implementation using scan and pagination), upstream PR pending, needs special handling for redis sentinel (and cluster...)
• ttlcache (a new go micro store wrapper around github.com/jellydator/ttlcache/v2, maybe v3), it supports a Loader mechanism which we need to pass using the Context of the go micro store interface.

The ocmem implementation supports a size limit, which we need to pass using the Context of the go micro store interface.

[butonic]

cc @aduffeck