Add integration test which uses latest-built compiler

[ronshapiro]

#994 identified an issue where we forgot to shade the dagger-spi artifact. Our tests never found this since they don't use maven. We should have a test that runs util/install-local-snapshot.sh and then runs a maven build with the LOCAL-SNAPSHOT build.

Either that, or a way in our release script to verify that we are correctly shading everything.

[ronshapiro]

This may now be as simple as just:

bazel test //...
bazel build //java/dagger/internal/codegen:new_bootstrap_compiler_deploy.jar
cp bazel-bin/java/dagger/internal/codegen/new_bootstrap_compiler_deploy.jar java/dagger/internal/codegen/bootstrap_compiler_deploy.jar
bazel test //...

[bcorso]

Closing this, since we added these tests a while ago, e.g. https://github.com/google/dagger/blob/master/util/run-local-tests.sh#L16-L33, and also a blaze rule for validation of deps, https://github.com/google/dagger/blob/master/tools/maven.bzl#L226