Unfortunately there is no test, as Bazel has not supported testing with
android_test yet, see https://github.com/bazelbuild/bazel/issues/903.
I'll add tests once we sync this to Google internal.

Also move AWS KMS integration code to integration.awskws and GCP KMS to
integration.gcpkms.

Change-Id: Idb715310f870a975ca6bcd2a314618680ab91fb9
ORIGINAL_AUTHOR=Thai Duong <thaidn@google.com>
GitOrigin-RevId: dc397b0d2ad53deb6d98ce739626fce39a94e656