Pass more context to hook_file_metadata_table_items_alter()

As per #1628044-31: Implement magic for the table of attachments on issues -- instead of only passing $entity as context to hook_file_metadata_table_items_alter() why don't we pass all the context we've got, just like we do for hook_file_metadata_table_rows_alter()? Obviously, we wouldn't need $items inside $context, but it seems like all the rest of these might be useful/necessary in certain alter cases, and it costs us nothing to pass them all at once:

 *  - field: The field definition array.
 *  - instance: The field instance definition array.
 *  - entity: An object representing the entity the file field is attachted to.
 *  - entity_type: String with the type of entity the field is attached to.

Any objections?

Thanks,
-Derek