Merge forwardport of #12031 to 2.3-develop branch

Applied pull request patch https://github.com/magento/magento2/pull/12031.patch (created by @enriquei4) based on commit(s):
  1. bce7d56

Fixed GitHub Issues in 2.3-develop branch:
  - #6661: XHTML templates Don't Use Schema URNs (reported by @astorm)

Author: magento-engcom-team

app/code/Magento/Ui/view/base/ui_component/templates/container/default.xhtml

@@ -5,7 +5,7 @@
  * See COPYING.txt for license details.
  */
 -->
-<div xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="../../../../../../Ui/etc/ui_template.xsd">
+<div xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Ui:etc/ui_template.xsd">
     <div data-bind="scope: '{{getName()}}.areas'" class="entry-edit form-inline">
         <!-- ko template: getTemplate() --><!-- /ko -->
     </div>

app/code/Magento/Ui/view/base/ui_component/templates/export/button.xhtml

@@ -5,7 +5,7 @@
  * See COPYING.txt for license details.
  */
 -->
-<div xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="../../../../../../Ui/etc/ui_template.xsd">
+<div xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Ui:etc/ui_template.xsd">
     <div data-bind="scope: '{{getName()}}.areas'">
         <!-- ko template: getTemplate() --><!-- /ko -->
     </div>

app/code/Magento/Ui/view/base/ui_component/templates/form/collapsible.xhtml

@@ -5,7 +5,7 @@
  * See COPYING.txt for license details.
  */
 -->
-<div xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="../../../../../../Ui/etc/ui_template.xsd">
+<div xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Ui:etc/ui_template.xsd">
     <div data-role="spinner" data-component="{{getName()}}.{{getName()}}" class="admin__form-loading-mask">
         <div class="spinner">
             <span/><span/><span/><span/><span/><span/><span/><span/>

app/code/Magento/Ui/view/base/ui_component/templates/form/default.xhtml

@@ -5,7 +5,7 @@
  * See COPYING.txt for license details.
  */
 -->
-<div xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="../../../../../../Ui/etc/ui_template.xsd">
+<div xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Ui:etc/ui_template.xsd">
     <div data-role="spinner" data-component="{{getName()}}.areas" class="admin__data-grid-loading-mask">
         <div class="spinner">
             <span/><span/><span/><span/><span/><span/><span/><span/>

app/code/Magento/Ui/view/base/ui_component/templates/listing/default.xhtml

@@ -9,7 +9,7 @@
     class="admin__data-grid-outer-wrap"
     data-bind="scope: '{{getName()}}.{{getName()}}'"
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-    xsi:noNamespaceSchemaLocation="../../../../../../Ui/etc/ui_template.xsd">
+    xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Ui:etc/ui_template.xsd">
     <div data-role="spinner" data-component="{{getName()}}.{{getName()}}.{{spinner}}" class="admin__data-grid-loading-mask">
         <div class="spinner">
             <span/><span/><span/><span/><span/><span/><span/><span/>