Add a new validation check for site coordinates during creation

Following up on the issue : https://github.com/aodn/issues/issues/1594, it has been agreed that we need to add new checks to the “New Site” form to:
- ensure that  -90.0<latitude<90.0 and -180.0<longitude<180.0
- latitude and longitude are not null  

so that missing or invalid coordinates raise an error when creating a new site.

see  related PR https://github.com/aodn/backlog/issues/7955