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.
Change beforeEachBindings to beforeEachProviders but preserve the
@deprecated method beforeEachBindings, in order to keep a working
deprecation warning
