Reformat Loggers

This MR is related to https://gitlab.inria.fr/melissa/melissa-combined/-/merge_requests/26. While adding a logger for deep learning experiment we noticed inconsistency in the current logging approach.

• No logger at the module level was being used (logging.getLogger(__name__)).
• Logged information were inconsistently formatted (using either f strings or format).

This MR brings the following changes:

• There is one log file melissa_launcher.log that is created in the launching directory for everything related to the launcher.
• There is one log file melissa_server.log that is created in the experiment directory for everything related to the server.
• (With https://gitlab.inria.fr/melissa/melissa-combined/-/merge_requests/26 there will be additionally the Tensorboard logs)
• Log control is centralized and format is standardized.