feat: add timezone message and timezones service

[jmnavarrete]

This pull request includes several changes to add support for timezones in the scheduling system. The most important changes include adding new message and service files, as well as updating existing message definitions to include timezone information.

Additions to message and service files:

• CMakeLists.txt: Added Timezone.msg to the list of message files and Timezones.srv to the list of service files. [1] [2]

Updates to existing message definitions:

• msg/EventScheduler.msg: Renamed date_start and date_end to start_date and end_date, respectively, and added a new timezone field.

New message and service definitions:

• msg/Timezone.msg: Added a new message definition with fields zone and offset.
• srv/Timezones.srv: Added a new service definition with fields timezones, success, and message.…essage