Verify ingest can be rejected because of large HTTP request body size

[Masih H. Derkani]

verify-ingest command uses POST to /multihashes endpoint with a fixed batch size of 4096. Depending on the kind of multihashes being verified the batch size alone is not enough to assure that the HTTP request body size is within the range accepted by an indexer. For example, cid.contact instances use nginx as the ingress controller with default request size of 1MiB.

As a result verifications can fail with status code 400 which can be confusing.

Instead of a fixed batch size, consider batching multihashes by a given max request body size and allow the clients to override the max body size with a default of 1MiB.