soroban-rpc: Audit and standardize logging

[paulbellamy]

What problem does your feature solve?

Currently the logging in soroban-rpc is a bit ad-hoc. We should audit what we have, and standardize it for better ingestion by people & other tools.

What would you like to see?

• Standardize the logging output format
• Standardize the logging severity we use for different info/warnings/errors
• Add a --log-level flag so operators can use what level of logging output they want.
• Add clear logging during startup so we have tools in-place to debug any potential issues there, and can understand where the service is in the startup process.
• Log all incoming jsonrpc method requests and their resolution.
  • Note, this should be two log entries, one when the request is received, and another one when it is completed, tied together with a request id. (Paul's opinion)
• Log all incoming http requests and their response with duration, etc.
• Add support for json log formatting (should this be a flag? default?)
• Audit to make sure the log outputs do not include any avoidable identifying information, or secrets.

What alternatives are there?

[2opremio]

Closing, I think I've covered everything in this ticket. @paulbellamy please reopen if you think otherwise.