cxx: naming refactor

• Moves message/satellite_definitions to utils/CSCP_definitions - I think this is more consistent (e.g. chirp/CHIRP_definitions) and I also think the namespace fits better (although not ideal).
• Also moves the two functions from satellite/fsm_definitions.hpp to that header.
• Also improves the regex expressions:
  • Satellite name: alphanumerical+underscore+not-empty: \w+ (\w is [_0-9a-zA-Z] and thus contains \d)
  • Command name: alphanumerical+underscore+start-with-non-digit: \D\w* (\D is [_a-zA-Z])
  • Run ID: alphanumerical+underscore+dashes+not-empty: [\w-]+
• Moves core/logging to core/log for better consistency with the namespace

As an alternative to moving CSCP_definitions to the utils namespace, we could also rename the message namespace to protocols and keep it there - I actually think this fits even better, even though we mostly only have message classes in there.