Automatic merge from submit-queue (batch tested with PRs 48292, 48121)

Add Google cloudkms dependency, add cloudkms service to GCE cloud provider

Required to introduce a Google KMS based envelope encryption, which shall allow encrypting secrets at rest using KEK-DEK scheme.

The above requires KMS API to create/delete KeyRings and CryptoKeys, and Encrypt/Decrypt data.

Should target release 1.8

@jcbsmpsn 

Update: It appears that Godep only allows dependencies which are in use. We may have to modify this PR to include some Google KMS code.

Progresses #48522