New RA that manage IP moving in GCP

This Resource Agent uses the GCP API to move a floating IP addresse within a
GCP VPC by changing an entry in the routing table, as discussed in the
documentation :
https://cloud.google.com/solutions/best-practices-floating-ip-addresses#option_4_failover_using_routes_api_calls

This agent also configures the floating IP locally on the instance OS.