[generic-config-updater] Improving CreateOnly validator and marking /LOOPBACK_INTERFACE/LOOPBACK#/vrf_name as create-only#1969

ghooo merged 3 commits intosonic-net:mastersonic-net/sonic-utilities:masterfrom

ghooo:dev/mghoneim/createonlyupdateghooo/sonic-utilities:dev/mghoneim/createonlyupdateCopy head branch name to clipboard