server: logs - unified format and --log-format option (#5700)

server: logs - unified format and --log-format option (#5700)

* server: logs - always use JSON logger, add add thread_id in message, log task_id and slot_id

* server : skip GH copilot requests from logging

* server : change message format of server_log()

* server : no need to repeat log in comment

* server : log style consistency

* server : fix compile warning

* server : fix tests regex patterns on M2 Ultra

* server: logs: PR feedback on log level

* server: logs: allow to choose log format in json or plain text

* server: tests: output server logs in text

* server: logs switch init logs to server logs macro

* server: logs ensure value json value does not raised error

* server: logs reduce level VERBOSE to VERB to max 4 chars

* server: logs lower case as other log messages

* server: logs avoid static in general

Co-authored-by: Georgi Gerganov <redacted>
* server: logs PR feedback: change text log format to: LEVEL [function_name] message | additional=data

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Co-authored-by: Georgi Gerganov <redacted>