package:test v1.25.3

• Remove outdated StreamMatcher link from README table of contents.
• Document the silent reporter in CLI help output.
• Support enabling experiments with the dart2wasm compiler.
• Added @doNotSubmit to test(solo: ...) and group(solo: ...). In
  practice, this means that code that was relying on ignoring deprecation
  warnings and using solo or group with a skip parameter will now fail if
  dart analyze --fatal-infos (or similar) is enabled.