Check all ancestor navigable trustworthiness for mixed content (#36157)

Propagate through documents a flag that represents if any of the
ancestor navigables has a potentially trustworthy origin.

The "potentially trustworthy origin" concept appears to have gotten
confused in a couple of places and we were instead testing if a URL had
"potentially trustworthy" properties.

The main test for the ancestor navigables is
[mixed-content/nested-iframes](https://github.com/web-platform-tests/wpt/blob/master/mixed-content/nested-iframes.window.js)

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---------

Signed-off-by: Sebastian C <sebsebmc@gmail.com>

components/script/dom/htmlformelement.rs

@@ -867,6 +867,7 @@ impl HTMLFormElement {
             target_document.get_referrer_policy(),
             Some(target_window.as_global_scope().is_secure_context()),
             Some(target_document.insecure_requests_policy()),
+            target_document.has_trustworthy_ancestor_origin(),
         );
 
         // Step 22