If the Media name is displayed on the create/edit form, make it not mandatory. If the name has been set previously or updated, preserve it on file change.

Preserve the default core behaviour:
- populate the name with the file name if it is left empty
- if it has the same name as the file name, update it on file update.

Example use case

For most Media types/bundles it does not make sense to expose the name field.
In some cases e.g. Documents, it could make sense to have a persistent file name even
if the file is replaced.