Add evaluation test to webdev to catch issues with runtime debugging API

[annagrin]

Test-only change.

Adding a test that will catch bugs like dart-lang/sdk#53459 once we have testing of webdev with stable SDK: #2226

[parlough]

I wanted to say thanks for thinking hard about how to improve coverage of this in general, but also specifically for the stable experience. package:webdev and the experiences/debugging it enables can be tough since it's connecting a bunch of different tools/parts, all not necessarily at the same step. It's appreciated 💙