Windows has some strong limitations on command line arguments,
specially when it's too long. In the googlecloudstoragefixture anttask
the classpath argument is very long and the command fails. This commit
removes the classpath as an argument and uses the CLASSPATH
environment variable instead.
This commit adds a GoogleCloudStorageFixture that uses the
logic of a GoogleCloudStorageTestServer (added in #28576)
to emulate a remote Google Cloud Storage service.
By adding this fixture and a more complete integration test, we
should be able to catch more bugs when upgrading the client library.
The fixture is started by the googleCloudStorageFixture task
and a custom Service Account file is created and added to the
Elasticsearch keystore for each test.