Run tests in providers by default

[iwahbe]

We should run tests in the module rooted in providers by default. In GCP we do it with a pre-test hook. This should be the default.

[blampe]

Some providers currently put unit and integration tests under provider. We should certainly always run those unit tests, however we don't need two places for integration tests. Those should be consolidated somewhere -- typically "examples" but the name doesn't matter and this is configurable. In CDK we moved these to a tests directory.

Having one place for integration tests will simplify sharding and speed things up overall.