Modify the extract shorelines to not require transects

[2320sharon]

This modification of the extract_all_shorelines function would allow users to extract 2D shorelines even if no transects were provided.
If the user did not provide transects then none of the shoreline change along the transect files would be generated. This would also mean the user could not compute the tide correction. Only the files related to the 2D shorelines and the config files will be created in this scenario.

To make this change possible before the intersections with the transects are run the function would need to return. Additionally, the function validate_extract_shoreline_inputs , which is called in the extract_all_shorelines function would need to modified to not raise an error if the transects are not present. The rest of the workflow would need to be tested to make sure no other processes break if no transects are present.