Bug 1567348 [wpt PR 17917] - Make XSLT IDL source and idlharness.js test tentative, a=testonly

Automatic update from web-platform-tests
Make XSLT IDL source and idlharness.js test tentative (#17917)

* Rename xslt.idl to xslt.tentative.idl

This is to avoid it being removed by the reffy-reports sync process:
https://github.com/web-platform-tests/wpt/pull/17847

* Update and rename idlharness.window.js to idlharness.tentative.window.js

--

wpt-commits: 91fd78875c637702d8f30b95298b52fbec7cfdd2
wpt-pr: 17917


--HG--
rename : testing/web-platform/tests/interfaces/xslt.idl => testing/web-platform/tests/interfaces/xslt.tentative.idl

testing/web-platform/tests/xslt/idlharness.tentative.window.js

@@ -4,7 +4,7 @@
 'use strict';
 
 idl_test(
-  ['xslt'],
+  ['xslt.tentative'],
   ['html'],
   async idlArray => {
     idlArray.add_objects({