Fix bugs of ACF and featured media

[ixkaito]

This PR fixes the following.

• wp_make_content_images_responsive() is deprecated and the wp_make_content_images_responsive hook was removed.
  • Use wp_filter_content_tags() and the wp_filter_content_tags hook instead.
• Fix ACF bug with repeater fields
  • We are using the wrong hook to get the value. We have to get the value before formatted and overwrite it after formatted via acf/format_value/type={$type}.
• Fix bugs of saving featured images via REST API (i.e. Block Editor)
  • We have to use the rest_pre_insert_{$post_type} hook to get the featured image ID

[jonnyvaughan]

Thank you!