[WIP] Feature/1753 search tab v2

[doekenorg]

This is a rebased PR on top of develop for #1753.

Todo:

Small-ish:

• [x] Sieve individual choice fields
• [x] Add search mode field (hidden / choice) with a default option
• [x] Make "Only for logged-in users" option work
• [x] Apply custom classes to fields
• [x] "Advanced Search" toggle rework (and open when one of the fields when it is actively used in the search)
• [x] Add Search Everything / Search Mode (hidden) / Search Button as a default configuration
• [x] Move entire row between search sections
• [ ] Add setting to opt-in to new search templates
• [ ] Reset Widget on form/view change
• [ ] Prevent duplicate fields (?)
• [ ] Fix Populate Anything on choices

Larger:

• [x] Store the settings per widget instead of one per view
• [ ] Migrate old configuration to new configuration (should be possible on-the-fly)
  • [ ] Add Search button if it is missing
  • [ ] Add hidden Search Mode field with the stored setting as default
  • [ ] Vertical is a single column, Horizontal is 2 columns (split odd/even)
• [ ] Add new search templates with nicer styling
• [ ] Fix tests

Separate feature:

• [ ] Search settings (This was part of Search everything, but it doesn't make sense. We cannot force this from the widget as there might be multiple.
  • [ ] Include meta fields (ID, etc)
  • [ ] Exclude hidden fields

Caveats:

• gravityview_widget_search_filters will be run at least twice with an additional $position (general/advanced)
• gravityview/search/sieve_choices should still work
• gravityview_search_field_label should still work
• gravityview/search/filter_details should still work
• Look into permalinks option on the widget-search.php template

New features:

• Layout Builder for Search Fields
• Search Mode field (customer can toggle, or field is hidden (default))
• Search Button field (place it anywhere)
• Sieving on individual fields instead of all of them
• Search Field visibility on caps
• Advanced Search Fields dropdown