Add support for default values in the Repeater interface

Describe the Bug The current implementation of default values for Repeater fields in Directus has a significant limitation: the default value applies only to the initial state of the entire Repeater field (e.g., the first entry). However, when a new item is added to the Repeater, all fields within that new entry are empty, as the default value cannot be defined for the individual fields inside the Repeater structure. Current behavior: • The default value initializes the Repeater field with one prefilled entry, but does not affect any subsequent entries. • Users must manually fill in all fields for every new entry, even if consistent default values are required for each added item. Proposed enhancement: • Allow specifying default values for the individual fields inside the Repeater structure. • These defaults would be applied automatically whenever a new entry is created within the Repeater. This enhancement would significantly improve usabil…