Support for YANG Actions

Introduction of gRPC Actions modeled with YANG. This includes: ping, traceroute, bgp, ospf, ospfv3, isis, snmp-test-trap, syslog, cfgmgr-rollback, crypto, lib-keychain, hwmod-mpa-reload, infra-statsd, sysmgr, upgrade-fpd-ng. Take a look at the YANG repo for details: yang/vendor/cisco/xr/641.