[CoPP] Add always_enabled field to coppmgr logic (sonic-net#2034)

- What I did
Add the new design for copp manager - always_enabled field in copp_cfg.json file.

- Why I did it
A change was done for traps needs to be installed but doesn't have feature (arp, udld, lacp, ip2me),
in the new implementation, coppmgr will not automatically install traps which has no entry in features table, but will check first if the trap has "always_enabled":"true" field.

- How I verified it
run tests for making sure traps are installed and not when expecting them to.

- Details if related
Related to sonic-buildimage change - sonic-net/sonic-buildimage#9302
SONiC mgmt test plan can be found in sonic-net/SONiC#903.

Author: noaOrMlnx