Fix OpenFGA cluster issues

[stgraber]

This fixes a number of problems with the initial OpenFGA implementation:

• Race condition where all cluster members attempt to sync all resources, this is very wasteful and the code itself is racy, leading to some write conflicts. This PR restricts the resource sync to the cluster leader.
• Storage bucket deletion was going through access control twice for some reason
• Storage volumes are updated to allow for an optional location field
• Storage buckets are updated to allow for an optional location field

Closes #265

[stgraber]

This turned out a tiny bit harder than first expected as it requires knowing whether we're clustered in a few new places. To do this consistently and easily, I've now moved the clustering state to the shared state struct.