Fixes #6907 -- display_filter always set to the_title for Display Field in Selection List

[therealgilles]

Description

This fixes the filter applied to the Display Field in Selection List field when applicable. Before this fix, the default the_title filter was applied to the field, even though it may not have been applicable. An example is if the field value is set to {@permalink} to display the field as a slug (i.e. post_name).

Related GitHub issue(s)

Fixes #6907.

Testing instructions

See #6907.

Screenshots / screencast

Changelog text for these changes

Bug:$display_filter needs to be computed with the updated $field_index value. #6907

PR checklist

• I have tested my own code to confirm it works as I intended.
• My code follows the WordPress Coding Standards.
• My code follows the WordPress Inline Documentation Standards.
• My code includes automated tests for PHP and/or JS (if applicable).

[therealgilles]

@JoryHogeveen In the code below:

              $display_filter_args = pods_v( 'display_filter_args', pods_v( $field_index, $search_data->pod_data['object_fields'] ) );

Is $search_data->pod_data['object_fields'] the same as $search_data->object_fields? If so, this line could be replaced with:

              $display_filter_args = pods_v( 'display_filter_args', $display_filter ) );

which would make most sense.