Define a custom script dataType converter, don't override the base one

The jquery upgrade from 2.2.4 to 3.7.1 from 16cf008
was causing a 401 unauthorized with sso enabled with kerberos to spin the login page
because our script converter wasn't being run, therefore we weren't processing the
response payload from the 401, which should update the page with the error, stop the
spinner, and show the login fields.

There were some changes in the 2.2.4 to 3.7.1 jquery upgrade  that seems to conflict
with our converter, perhaps our converter was being overridden, or maybe we need to
override it differently.  Either way, we can avoid this by defining our own converter.

This was recreated locally via:

render :inline => Rails.root.join("public/proxy_pages/invalid_sso_credentials.js").read, :content_type => "text/javascript", :status => 401
in kerberos_authenticate in dashboard_controller.rb and running this in the js console:

await miqAjaxAuthSso('/dashboard/kerberos_authenticate?button=sso_login');

Here are the full set of changes for the upgrade:
jquery/jquery@2.2.4...3.7.1

Author: jrafanie

app/javascript/oldjs/jquery_overrides.js

@@ -36,7 +36,7 @@ $.ajaxSetup({
         return jQuery.parseJSON(text);
       });
     }),
-    'text script': logError(function(text) {
+    'text miq_script': logError(function(text) {
       if (text.match(/^{/)) {
         return jQuery.jsonPayload(text, function(text) {
           return text;

app/javascript/oldjs/miq_application.js

@@ -1123,8 +1123,8 @@ window.miqJqueryRequest = function(url, options) {
   };
 
   if (options.dataType === undefined) {
-    ajax_options.accepts = { script: `*/*;q=0.5, ${$.ajaxSettings.accepts.script}` };
-    ajax_options.dataType = 'script';
+    ajax_options.accepts = { miq_script: `*/*;q=0.5, ${$.ajaxSettings.accepts.script}` };
+    ajax_options.dataType = 'miq_script';
   }
 
   // copy selected options over