Add a DEV MODE option for declaring sim beamline imports for running in simmode locally

This function looks for the BEAMLINE environment name and then tries to import the associated dodal module. When running in dev mode, the BEAMLINE environment variable isn't set, and there would be no module to import. This means we are currently unable to start hyperion in dev mode. A quick solution would be to default to importing the i03 module if we're running in dev mode.

## Acceptance Criteria
* Implement a way to get `get_beamline_based_on_environment_variable() ` in developer mode
* Ensure `hyperion.sh --skip-startup-connection` runs succesfully after doing this change (with no errors in` hyperion/tmp/dev/start_log.txt`)