Tweak wait_until option

Small tweaks to https://github.com/lightpanda-io/browser/pull/1896

Improve the wait ergonomics with an Option with default parameter. Revert
page pointer logic to original (don't think that change was necessary).

src/cdp/testing.zig

@@ -136,7 +136,7 @@ const TestContext = struct {
                 0,
             );
             try page.navigate(full_url, .{});
-            _ = bc.session.wait(2000, .load);
+            _ = bc.session.wait(.{});
         }
         return bc;
     }