selenium images should be cross-platform now that chromium package is available on arm64

### Which image/versions are related to this issue/feature request? I believe all of the `selenium-*` images should be able to be cross-arch now: - chainguard-private/selenium-base - chainguard-private/selenium-distributor - chainguard-private/selenium-event-bus - chainguard-private/selenium-hub - chainguard-private/selenium-node-base - chainguard-private/selenium-node-chromium - chainguard-private/selenium-node-docker - chainguard-private/selenium-node-firefox - chainguard-private/selenium-router - chainguard-private/selenium-session-queue - chainguard-private/selenium-sessions - chainguard-private/selenium-standalone-chromium - chainguard-private/selenium-standalone-docker - chainguard-private/selenium-standalone-firefox ### Issue/Feature description When we added `arm64` support for the `chromium` package and image a few months ago, we did not also update the selenium packages so those images are still intel-only. Can we please enable multi-arch builds for as many of these selenium images as possible? Thank you.