Enhance Logging capabilities

[MagnusBadelHacon]

Hello,

I don't know if this is the correct place to raise this ticket or if you'd like a Jira ticket, please raise this point here if this is inappropriate.

I had a look at the current capabilities for logging in the C++ SDK for Couchbase and to me there is a gap. I'd like to the pass in my own logging callback - I.e. a lambda that receives a log line to do some processing. The context for this that I want to be able to log into different systems (i.e. SysLog or similar) or into a legacy application specific logger (meaning not spdlog). Currently this gap blocks us from using the C++ SDK over the C SDK.

Best regards, Magnus