Add edit functionality for mount actions

In https://gitlab.hzdr.de/hub-terra/sms/frontend/-/issues/268 we improvements in the way to add mounts. Now, we need to improve the functionality to edit them again - mostly due to the database change to combine mount & unmount information.

So we want:

• a form to edit the offsets, begin date, end date, descriptions & contacts.
• that we still check for the parent platform mount (parent must be mounted for the whole timespan)
• check dynamic location actions (if a devices measured quantity is still needed for the location action)
• simple to reach this form (idea is to have it as an element in a three dot menu in the row of the configuration tree)
• make it clear that the offsets are still relative to the parent platform

For the moment there is no need in deleting mount actions.