Refactor team leader name handling in MGX environment

[BJeff17]

This pull request updates the handling of the team leader's name within the MGXEnv class to make it configurable instead of hardcoded. Instead of always using "Mike" as the team leader, the name can now be set dynamically, improving flexibility for different team configurations.

Team leader name configuration:

• Added a new attribute team_leader_name to the MGXEnv class, allowing the team leader's name to be changed from the default ("Mike") as needed.
• Updated the publish_message method to use self.team_leader_name instead of the hardcoded team leader name when retrieving the role.
• Modified the move_message_info_to_content method to reference self.team_leader_name when displaying message recipients, ensuring consistency with the configurable team leader name.