[Test Gap][BGP][T2] Missing specific cases of TSA on sup effect on LCs

[Javier-Tan]

Test Gap Description

The following behaviour is not being tested:

• If Supervisor tsa_enabled == TRUE, operational state is TSA(TRUE). In this configuration
  • A. After the Line card reboots - the operational state will be TSA when the Line card comes back up. The "startup_tsa_tsb" service will still set the local CONFIG_DB attribute and start a timer. If the timer expires while Supervisor is still "tsa_enabled", the operational state will still be TSA.
  • D. The Line Card "startup_tsa_tsb" service will still kick-in after a LC reboot After a Line Card

This is defined/stated in https://github.com/sonic-net/SONiC/blob/master/doc/voq/Reliable_TSA.md

Test Plan

Add testcase to test_startup_tsa_tsb_service.py to test LCs still execute startup_tsa_tsb service
and remain in TSA state after startup_tsa_tsb service is finished

Test environment

Topology: T2

Attach files (if any)

N/A

[Javier-Tan]

@arlakshm for vis

[Javier-Tan]

Reducing scope as #13290 covers the rest of what I thought was missing