[action] [PR:12931] Skip iface loopback test if Leaf-fanout switch is running SONiC and Mellanox ASIC

[mssonicbld]

Description of PR

Summary:
The test cases in test_iface_loopback_action.py is failing consistently on some testbed when the leaf-fanout is Mellanox and running SONiC. This is because the test sends packets with Vlan tag for testing, while TPID is not supported on Mellanox if running SONiC OS.
So the test needs to be skipped in the above setup.

Type of change

• Bug fix
• Testbed and Framework(new/improvement)
• Test case(new/improvement)

Back port request

• 201911
• 202012
• 202205
• 202305
• 202311

Approach

What is the motivation for this PR?

This PR is to skip test_iface_loopback_action.py if the leaf-fanout is Mellanox and running SONiC.

How did you do it?

Add a fixture to check OS and ASIC of leaf-fanout switch.

How did you verify/test it?

The change is verified on a physical testbed.

collected 3 items 

iface_loopback_action/test_iface_loopback_action.py::test_loopback_action_basic SKIPPED (Not supporteds on Mellanox leaf-fanout running SONiC) [ 33%]
iface_loopback_action/test_iface_loopback_action.py::test_loopback_action_port_flap SKIPPED (Not supporteds on Mellanox leaf-fanout running SONiC) [ 66%]
iface_loopback_action/test_iface_loopback_action.py::test_loopback_action_reload SKIPPED (Not supporteds on Mellanox leaf-fanout running SONiC) [100%]

Any platform specific information?

Mellanox platform specific.

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

Not a new test case.

Documentation

[mssonicbld]

Original PR: #12931