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/navigation.rs

@@ -212,6 +212,7 @@ impl InProgressLoad {
                 .inherited_insecure_requests_policy
                 .unwrap_or(InsecureRequestsPolicy::DoNotUpgrade),
         )
+        .has_trustworthy_ancestor_origin(self.load_data.has_trustworthy_ancestor_origin)
         .headers(self.load_data.headers.clone())
         .body(self.load_data.data.clone())
         .redirect_mode(RedirectMode::Manual)