[flutter] Add web_tool_tests suite

See https://github.com/flutter/flutter/pull/70226.

Change-Id: I53f9b5042b7d3b0b50be496ce76b9286e24e8625
Reviewed-on: https://dart-review.googlesource.com/c/recipes/+/173780
Auto-Submit: Alexander Thomas <athom@google.com>
Reviewed-by: Karl Klose <karlklose@google.com>
Commit-Queue: Karl Klose <karlklose@google.com>
4 files changed