Additional test cases to verify 'startup_tsa_tsb.service' - PR#18496 …

…PR#12238 (#12781)

This PR has additional new test cases to verify the changes introduced as part of # Linecard startup-TSA-TSB sonic-buildimage#18496.
This PR is dependent on PR Tests to verify 'startup_tsa_tsb.service' during linecard bring up - PR#18496 #12238
Basically, this PR has new 4 test cases in addition to the 5 test cases added to verify start and stop of the new service 'startup_tsa_tsb.service' introduced by PR Tests to verify 'startup_tsa_tsb.service' during linecard bring up - PR#18496 #12238