The Durable Object runtime now passes through the name used with
`idFromName`, so it is available inside the DO constructor via
`state.id().name()` (cloudflare/workerd#2240).

Previously `get_durable_object_name` brute-forced the name by enumerating
every configured log (and batcher shard) and comparing `id_from_name`
results against the DO's id. Replace it with the runtime-provided name:

- Sequencers and cleaners are unsharded, so their DO name is the base log
  name; they read `state.id().name()` directly.
- Batchers are always addressed with a shard suffix (`{name}_{shard_id:x}`),
  so a new `get_sharded_durable_object_base_name` helper strips the trailing
  `_{shard_id:x}` component to recover the base log name.