Design and implement testing strategy for web app components

[srawlins]

Likely using webdriver and pageloader.

CC @parlough @devoncarew

[srawlins]

@yjbanov pointed me to https://github.com/flutter/engine/blob/main/lib/web_ui/dev/webdriver_browser.dart for the infra for Flutter Web's webdriver testing.

[srawlins]

Then again, maybe an out-of-the-box Hybrid test from the test package will work. https://pub.dev/packages/test#browservm-hybrid-tests. I'm going to look into this first.

[srawlins]

After implementing this hybrid style test, I think it is not what we are looking for, as we need to send keys into the text field. I think we want a straight up black-box WebDriver test.

[srawlins]

I'm doing a browser tab cleanup and just need to leave a note that I was looking into DDS's smoke test w.r.t. this idea. I cannot remember any details, so just posting a link: https://github.com/dart-lang/sdk/blob/main/pkg/dds/test/sse_smoke_test.dart