Allow exposed form to preserve URL query parameters

Tested #34 with Facets. Steps:

1. Go to edit the views of interest
2. Expand "Advanced" section
3. Click "Exposed form style: Settings"
4. Put f in the Preserve query parameters from URL
5. Save and clear cache

It works.

Tested #36 Works Great (this feature should definitely be added)

+1 (awesomesauce) saved me from having to use hook_form_views_exposed_form_alter() to modify the submitted query parameters for the exposed filter.

Specifically useful when having other view blocks on page that use contextual filters with setting "provide default value" -> "Type: Query parameter" which updates the content in those blocks when the set parameters are passed by URL from custom links that provide those additional parameters.

#36 works for me as well.

I've added the code back from #34 and created an interdiff with #36.

Still need to address point 2 and 3 from #32

Patch from #42 is working well for me, we have a search implementation that has custom query parameters that were being lost on exposed form search. Although that's not specifically facets, but I believe the issue is the same.

Confirming the issue with Better Exposed Filters described in #33. Somehow, when BEF is used, the value already comes as an array. Attaching a patch with a fix.

The patch in #45 applies and works with D10.2.5.

But only with a Exposed form style:Basic (Exposed form in block:no)

It does not work with: Basic (with layout)

The extra empty parameter check from #36 and added in #42 broke the handling of array parameters (such as facets) for me. I've fixed it by first cleaning the variable mixing and then deleting this check as It looks to me that is already handled in
if (!isset($form[$name]) && !empty($query[$name]) && ($value = $query[$name]) !== '') {

The existence of this patch initially troubled me into thinking I need this patch but for the specific use case this issue was created I think we are already fine using the Search API module. Unless you are using facets without indexed views (using search_api) which I think is not possible...

The functionality was already built in #2378945: Facets are lost by Views on keyword search → and it's provided - without using any patches - in the Query settings form:

So the main question here is... do we still need issue?

Another use case where this patch is useful: https://www.drupal.org/project/calendar_view/issues/3403103 💬 Stay on same month/week after exposed filtering Needs review

I add 💬 Stay on same month/week after exposed filtering Needs review as a related issue then. But if we are to do anything in Drupal core, we have to update the issue summary since the initial one (using search_api & facets) is not valid anymore.