Enhance link event damping HLD

[Ashish1805]

• Update the unit of config parameter.
• Update the CLI format.

[Ashish1805]

cc: @bhagatgit @eddyk-nvidia @mikeberesford

[Ashish1805]

Adding @Junchao-Mellanox for review.

[DavidZagury]

@Ashish1805 - Is there a PR for sonic-mgmt with tests that will covers this feature? Is there a plan to add such tests?

[Ashish1805]

@Ashish1805 - Is there a PR for sonic-mgmt with tests that will covers this feature? Is there a plan to add such tests?

We dont have any sonic-mgmt test planned for the feature. Can you point to any sonic-mgmt tetss for any existing feature for reference? Thanks.

[DendroLabs]

Hi @Ashish1805 and @DavidZagury,

This PR has been inactive for over 2 years. I'm picking up the link event damping feature and driving it to completion.

@DavidZagury -- you asked about sonic-mgmt test coverage. I've drafted a comprehensive test plan with 38 test cases covering configuration, functional dampening behavior, CLI (show/clear), counters, monitor-only mode, syslog verification, edge cases, and scale testing on the vs platform. I'll include it when I open the implementation PRs.

I also plan to update the HLD with:

• Industry-standard recommended defaults (Cisco/Juniper: half-life=5s, reuse=1000, suppress=2000, max-suppress=20s)
• show interfaces dampening command specification
• sonic-clear interfaces dampening command specification
• YANG model additions for sonic-port.yang

Additionally, based on a review of operator complaints across Cisco, Juniper, and Arista forums, I'm proposing two enhancements that address the top industry pain points:

1. Syslog on suppress/unsuppress -- The most common complaint across all vendors is that dampening operates silently. Syncd will emit WARNING on suppress and NOTICE on unsuppress.

2. Monitor-only mode (algorithm="aied-monitor") -- RFC 7196 recommends a "Calculate But Do Not Damp" capability so operators can tune parameters without risking production outages. No vendor has implemented this. In monitor mode, penalties are calculated, STATE_DB is updated, and syslog messages are emitted, but events are NOT suppressed.

Will credit @Ashish1805 as original author of the HLD.