Align Core service logs.

[jrobinAV]

Description Here is an example of the logs generated by running a core service, executing two tasks and stopping the service.

[2024-02-07 10:27:44][Taipy][INFO] Start job dispatcher...
[2024-02-07 10:27:48][Taipy][INFO] job JOB_arima_training_7d61b95e-4998-4696-953b-ff74179f06b3 is completed.
[2024-02-07 10:27:49][Taipy][INFO] job JOB_arima_scoring_9c374054-cd38-4abf-82bd-28f43c33de56 is completed.
[2024-02-07 10:27:49][Taipy][INFO] Core service has been stopped.

Running the core service actually adds a log about starting a job dispatcher.

1. This is inconsistent regarding the log generated when stopping the service,
2. Running the core service does more than just starting a job dispatcher

Any change on that should be reflected in the documentation (user manual, reference manual, demos, tips and tricks, etc...)

Solution proposed Remove the log "Start job dispatcher..." and add a new log "Core service started..."

Acceptance Criteria

• [ ] The log should be consistent and representative of what is done.
• [ ] Ensure new code is unit tested, and check code coverage is at least 90%
• [ ] Ensure the documentation sets are updated