Issue #3554517: Fix api_key field definition to prevent data loss
The api_key base field definition was incomplete, causing API keys to be silently cleared when users are edited/saved. This adds the missing configuration methods to ensure proper field handling:
- setRevisionable(FALSE): API keys should not be revisioned
- setTranslatable(FALSE): API keys should not vary by language
- setDefaultValue(''): Explicit default value
- setDisplayConfigurable('form', FALSE): Prevent accidental form display
- setDisplayConfigurable('view', FALSE): Prevent accidental view display
This fix ensures the field is properly loaded from and saved to the database during entity operations.
Related to #3554517