[active-standby] support reset heartbeat suspend timer

[lolyu]

Description of PR

Summary:
Fixes # (issue)

Type of change

• Bug fix
• New feature
• Doc/Design
• Unit test

Approach

What is the motivation for this PR?

This is inspired from sonic-net/sonic-mgmt#16878; the active side could be stuck in the following loop if it cannot receive any heartbeats:

# (unknown, active, up) ----------------------------> (unknown, wait, up)
#         ^              suspend timeout, probe mux           |          
#         |                                                   |          
#         |                                                   |          
#         |                                                   |          
#         +---------------------------------------------------+          
#                mux active, suspend heartbeat with backoff

and the suspend timeout will backoff with max timeout as 128 * (negative retry + 1) * send interval; during this period, the mux port is unable to detect link failures as no heartbeats sending.
This PR is to support reset the suspend timer/backoff.

Signed-off-by: Longxiang Lyu [email protected]

Work item tracking

• Microsoft ADO (number only): 31339123

How did you do it?

Support reset heartbeat suspend timer for active-standby state machine.

How did you verify/test it?

UT

Any platform specific information?

Documentation

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