A restorer that keeps a hashtable mapping IDs to capabilities in memory.

create make_sturdy is a new in-memory-only table. make_sturdy id converts an ID to a full URI, by adding the hosting vat's address and fingerprint.

of_loader (module Loader) l is a new caching table that uses Loader.load l sr (Loader.hash id) to restore services that aren't in the cache.

add t id cap adds a mapping to t. It takes ownership of cap (it will call Capability.dec_ref cap on clear).

sturdy_ref t id is a sturdy ref that can be used to restore service id.

remove t id removes id from t. It decrements the capability's ref count if it was added manually with add.

clear t removes all entries from the table.