Prevent execution of (some) scripts moving between documents

This causes scripts that move between documents between the preparation
and execution phases to not execute, aligning with most browsers. Closes
#2469.

This does not address #2137, which is about scripts moving between
documents between the parsing and preparation, or parsing and execution
phases.

source

@@ -59614,6 +59614,9 @@ o............A....e
     href="https://github.com/whatwg/html/issues/2137">issue #2137</a>.</p>
    </li>
 
+   <li><p>If <var>scriptElement</var>'s <span>preparation-time Document</span> is not equal to
+   <var>document</var>, then return.</p></li>
+
    <li><p>If <span data-x="concept-script-script">the script's script</span> is null for
    <var>scriptElement</var>, then <span data-x="concept-event-fire">fire an event</span> named <code
    data-x="event-error">error</code> at <var>scriptElement</var>, and return.</p></li>