[Web Tools] Automated runner and tooling for Web integration tests #191315

Part of #191313

Problem

Running `package:integration_test` on Flutter Web requires manual `chromedriver` daemon management on port 4444 and complex `flutter drive` scripts. `flutter test integration_test -d chrome` is currently unsupported.

Solution

1. Provide a single-command CLI to run web integration tests headlessly in Chrome.
2. Automate `chromedriver` startup, port allocation, and process cleanup.
3. Support web renderers (`--web-renderer=canvaskit|skwasm`) and wasm compilation flags.
4. Capture browser console logs and failure screenshots on error.

Critical Edge Cases & Implementation Gotchas

• Headless Flag Dropping Bug (--web-run-headless does not take effect when using flutter drive for flutter web integration_test #95085): Existing `flutter_tools` implementation in `web_driver_service.dart` drops the `webRunHeadless` flag when recreating `DebuggingOptions`. Reusing or refactoring this path must fix or preserve headless configuration.
• Hermetic Binary Resolution (Formalize how to launch chrome and chromedriver in tests #187756): Avoid searching ambiguous `$PATH` locations for ChromeDriver. Respect standard environment variable overrides (`CHROMEDRIVER_EXECUTABLE`, `CHROME_EXECUTABLE`) for deterministic local and CI runs.
• CLI Option Friction (flutter drive options -d and --browser-name have confusing behavior #67090): Disambiguate `-d chrome` vs `--browser-name=chrome`; standardize on `-d chrome` as the first-class invocation.

Related Issues & Historical Context

• [Flutter drive/integration_test] improve commands experience #97519: [Flutter drive/integration_test] improve commands experience (Direct duplicate requesting automated ChromeDriver lifecycle; close on landing)
• Support running integration tests with the Flutter Tool #66264: [web] Flutter test should support integration test on web (Close on landing if implemented in `flutter_tools`)
• --web-run-headless does not take effect when using flutter drive for flutter web integration_test #95085: --web-run-headless does not take effect when using flutter drive for flutter web integration_test
• Formalize how to launch chrome and chromedriver in tests #187756: Formalize how to launch chrome and chromedriver in tests
• flutter drive options -d and --browser-name have confusing behavior #67090: `flutter drive` options `-d` and `--browser-name` have confusing behavior