Allow RemoteContextHelper to open windows from remote contexts

[chromium-wpt-export-bot]

There will be multiple tests in followup CLs that will need to open
windows from existing windows and frames. This will allow to simplify those tests.

Example usage: https://crrev.com/c/5841474

Bug: 340606651
Bug: b/365144247
Change-Id: I47f4d8c473fe69bc72e2c9345c0d5825451431e4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5838815
Commit-Queue: Ari Chivukula <arichiv@chromium.org>
Reviewed-by: Fergal Daly <fergal@chromium.org>
Reviewed-by: Ari Chivukula <arichiv@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1355331}

[wpt-pr-bot]

The review process for this patch is being conducted in the Chromium project.

[WeizhongX]

WPT Command: python3 ./wpt run --channel=nightly --verify --verify-no-chaos-mode --verify-repeat-loop=0 --verify-repeat-restart=10 --github-checks-text-file=/home/test/artifacts/checkrun.md --affected base_head --log-mach-level=info --log-mach=- -y --no-pause --no-restart-on-unexpected --install-fonts --no-headless --verify-log-full --binary=/home/test/build/firefox/firefox firefox

Some affected tests had inconsistent (flaky) results:

Unstable results

Test | Subtest | Results | Messages -- | -- | -- | -- /html/browsers/browsing-the-web/history-traversal/document-state.https.html |   | OK: 1/10, TIMEOUT: 9/10 |   /html/browsers/browsing-the-web/history-traversal/document-state.https.html | A navigation's initiator origin and referrer are stored in the document state and used on location.reload() | PASS: 1/10, TIMEOUT: 9/10 | Test timed out

These may be pre-existing or new flakes. Please try to reproduce (see the above WPT command, though some flags may not be needed when running locally) and determine if your change introduced the flake. If you are unable to reproduce the problem, please tag @web-platform-tests/wpt-core-team in a comment for help.

[WeizhongX]

https://wpt.fyi/results/html/browsers/browsing-the-web/history-traversal/document-state.https.html?label=experimental&label=master&aligned

This seems to be an existing flaky. @KyleJu @jcscottiii Can you help admin merge?