[test_auto_techsupport] Implemented auto-techsupport test cases (#5465)

Implemented auto-techsupport test cases which will validate auto-techsupport feature

- What is the motivation for this PR?
New tests added for new SONiC feature

- How did you do it?
Implemented new tests(see code)

- How did you verify/test it?
Executed new tests on latest master image

- Any platform specific information?

- Supported testbed topology if it's a new test case?
any

Signed-off-by: Petro Pikh <petrop@nvidia.com>