Should herald support --chain argument, or should the chain (aka env.coin) be inferred from DBState?

In most cases the DB (--db_dir=X) will have been populated by scribe, and so it's the *scribe* --chain=Y argument that's determinative.

```
(venv) swdev1@Jonathans-Mac-mini hub % herald --help
usage: herald [-h] --db_dir DB_DIR [--reorg_limit REORG_LIMIT] [--chain {mainnet,regtest,testnet}] [--max_query_workers MAX_QUERY_WORKERS] [--cache_all_tx_hashes] [--cache_all_claim_txos]
..snip...
optional arguments:
-h, --help show this help message and exit
--db_dir DB_DIR Path of the directory containing lbry-rocksdb.
--reorg_limit REORG_LIMIT
Max reorg depth
--chain {mainnet,regtest,testnet}
Which chain to use, default is mainnet, others are used for testing
...snip...
```

Start with the herald CLI shown in the issue and inspect how --db_dir, --chain, and DBState are handled, then compare that with the scribe --chain setting. Determine whether the chain can be reliably inferred from the database or whether the explicit argument must remain; done means the project has a decided behavior and corresponding documented or tested CLI expectations.

Written by the indexing model from the issue text.