Function createReplaceableLoader

createReplaceableLoader(
    store: EventStore,
    pool: ApplesaucePool,
    tiers: RelayTiers,
): AddressPointerLoader
The applesauce address loader kernl uses for replaceable and addressable events the store does not hold: it asks the pointer's relays, then the discovery tier, and adds what it finds to the store.
Parameters
- store: EventStore
  The shell's single event store.
- pool: ApplesaucePool
  The shared applesauce pool.
- tiers: RelayTiers
  Relay tiers; the discovery tier is the lookup fallback.
Returns AddressPointerLoader
A loader for createIdentityProviders and lookupReplaceable.
Example
```
const loader = createReplaceableLoader(eventStore, pool, tiers);
const lookupBefore = lookupReplaceable(eventStore, { loader, relays: () => tiers.get().outbox });
```