in memory datastore use extremely slow map datastore

https://github.com/ipfs/kubo/blob/f8f4b83c9c473ebd01e9624a39097a429f65c572/repo/fsrepo/datastores.go#L178

Many pieces of kubo implements table databases or other high level databases concepts by listing and sorting keys in the datastore.
The map datastore does not use any index, it literally just runs the complete matcher against all full keys by iterating a golang map, it's also very contentious.

We should change this to a badger or level in memory instead (because this what we happen to use already).