[Coppmgr] Disable traps that are not explicitly present in feature table

[prsunny]

Description

In the current design, Coppmgr checks the feature table for status before installing traps. Sometimes, the new traps may not be added to feature table or could be missed, and since the existing logic is to enable a trap, if the corresponding feature is not present, such new traps can get installed and orchagent may fail.

We need a logic change to disable the trap if the feature is not present and for legacy compatibility, the following traps can be hard-coded and installed.

[arp, lacp, udld, ip2me]

Steps to reproduce the issue:

1. Install a new trap for which feature table is not present

Describe the results you received:

Describe the results you expected:

Output of show version:

SONiC.20201231.22

Output of show techsupport:

(paste your output here or download and attach the file here )

Additional information you deem important (e.g. issue happens only occasionally):

[prsunny]

Assigned to @dgsudharsan

[prsunny]

The fix plan is as below:

1. The trap is checked against feature table. Any trap that needs to be installed should have the corresponding feature name enabled
2. For the legacy traps [arp, lacp, udld and ip2me], introduce a new attribute "always_enabled" to "true". This shall override the feature table check and gets installed irrespective of the feature table status.
3. There is no need of a config_db migrator as there are not traps saved to config_db in the current design.