[service] Revisit log levels #498

Describe the bug
The chainhook service has a lot of warn and error logs that probably should be debug or info, including but not limited to:

• The "unable to load chainhook associated with key {}" error when retrieving deleted predicates
• /new_mempool_tx/drop_mempool_tx/unimplemented observer endpoints should be debug
• Possibly predicate trigger failing?
• Attempting to set _ status when previous status was _