Call resetContextGroup on page removal

Calling it here ensures that the inspector gets reset on internal page
navigation. We were seeing intermittent segfaults on a problematic WPT tests
(/encoding/legacy-mb-japanese/euc-jp/) which I believe this solves.

(The tests are still broken. Because we don't support form targets, they cause
the root page to reload in a tight cycle, causing a lot of context creation /
destruction, which I thin was the issue. This commit doesn't fix the broken test
but it hopefully fixes the crash).

Also, clear out the Inspector's default_context when the default context is
destroyed. (This was the first thing I did to try to fix the crash, it didn't
work, but I believe it's correct).

src/cdp/domains/page.zig

@@ -290,6 +290,10 @@ pub fn pageNavigate(bc: anytype, event: *const Notification.PageNavigate) !void
 }
 
 pub fn pageRemove(bc: anytype) !void {
+    // Clear all remote object mappings to prevent stale objectIds from being used
+    // after the context is destroy
+    bc.inspector_session.inspector.resetContextGroup();
+
     // The main page is going to be removed, we need to remove contexts from other worlds first.
     for (bc.isolated_worlds.items) |isolated_world| {
         try isolated_world.removeContext();