Use a switch to toggle visibility to valuators

Using a checkbox wasn't very intuitive because checkboxes are
checked/unchecked when clicked on even if there's an error in the
request. Usually, when checkboxes appear on a form, they don't send any
information to the server unless we click a button to send the form.

So we're using a switch instead of a checkbox, like we did to
enable/disable phases in commit 46d8bc4f0.

Note that, since we've got two switches that match the default
`dom_id(record) .toggle-switch` selector, we need to find a way to
differentiate them. We're adding the `form_class` option for that.

Also note that we're now using a separate action and removing the
JavaScript in the `update` action which assumed that AJAX requests to
this action were always related to updating the `visible_to_valuators`
attribute.

app/components/admin/toggle_switch_component.rb

@@ -25,7 +25,11 @@ class Admin::ToggleSwitchComponent < ApplicationComponent
         method: :patch,
         remote: true,
         "aria-pressed": pressed?,
-        form_class: "toggle-switch"
+        form_class: "toggle-switch #{options[:form_class]}".strip
       }
     end
+
+    def html_options
+      default_options.merge(options.except(:form_class))
+    end
 end