Use data-chooser-modal-search-filter on collection filter mixin

So that document and image choosers don't have to identify it by ID in their JS

client/src/entrypoints/documents/document-chooser-modal.js

@@ -19,7 +19,6 @@ class DocumentChooserModalOnloadHandlerFactory extends ChooserModalOnloadHandler
 
 window.DOCUMENT_CHOOSER_MODAL_ONLOAD_HANDLERS =
   new DocumentChooserModalOnloadHandlerFactory({
-    searchFilterSelectors: ['#id_collection_id'],
     searchInputDelay: 50,
     creationFormFileFieldSelector: '#id_document-chooser-upload-file',
     creationFormTitleFieldSelector: '#id_document-chooser-upload-title',

client/src/entrypoints/images/image-chooser-modal.js

@@ -92,7 +92,6 @@ class ImageChooserModalOnloadHandlerFactory extends ChooserModalOnloadHandlerFac
 
 window.IMAGE_CHOOSER_MODAL_ONLOAD_HANDLERS =
   new ImageChooserModalOnloadHandlerFactory({
-    searchFilterSelectors: ['#id_collection_id'],
     creationFormFileFieldSelector: '#id_image-chooser-upload-file',
     creationFormTitleFieldSelector: '#id_image-chooser-upload-title',
     creationFormEventName: 'wagtail:images-upload',

wagtail/admin/forms/choosers.py

@@ -75,4 +75,5 @@ class CollectionFilterMixin(forms.Form):
                 label=_("Collection"),
                 choices=collection_choices,
                 required=False,
+                widget=forms.Select(attrs={"data-chooser-modal-search-filter": True}),
             )