chore(test): migrate Dart tests to package:test

Instead of running with karma and the karma-dart shim, run dart
tests directly using the new package:test runner. This migrates
away from package:unittest.

Fixes a couple tests, mostly associated with depending on absolute
URLs or editing the test providers after an injector had already
been created.

Remove karma-dart and associated files. Change gupfiles to run tests
via `pub run test` instead.

modules/benchpress/pubspec.yaml

@@ -13,7 +13,10 @@ dependencies:
   stack_trace: '^1.1.1'
   webdriver: '^0.9.0'
 dev_dependencies:
-  guinness: '^0.1.17'
+  guinness2: '0.0.4'
+  quiver: '^0.21.4'
+  test: '^0.12.10'
 dependency_overrides:
   angular2:
     path: ../angular2
+  matcher: '0.12.0+1'