[test gap] QoS tests are skipped on t1-64-lag topology

[bingwang-ms]

Description The test cases in qos subdirectory are skipped on Mellanox platform because LAG members are not allowed to be used.

 # LAG ports in T1 TOPO need to be removed in Mellanox devices
        if topo in self.SUPPORTED_T0_TOPOS or isMellanoxDevice(duthost):
            pytest_assert(
                not duthost.sonichost.is_multi_asic, "Fixture not supported on T0 multi ASIC"
            )
            for _, lag in mgFacts["minigraph_portchannels"].items():
                for intf in lag["members"]:
                    dutLagInterfaces.append(mgFacts["minigraph_ptf_indices"][intf])

            testPortIds = set(mgFacts["minigraph_ptf_indices"][port]
                                for port in mgFacts["minigraph_ports"].keys())
            testPortIds -= set(dutLagInterfaces)
            if isMellanoxDevice(duthost):
                # The last port is used for up link from DUT switch
                testPortIds -= {len(mgFacts["minigraph_ptf_indices"]) - 1}
            testPortIds = sorted(testPortIds)
            pytest_require(len(testPortIds) != 0, "Skip test since no ports are available for testing")

In t1-64-lag topology, all of the ports are in LAG. That means the test cases are always skipped on Mellanox device with t1-64-lag topology.

The skipped test cases are

testQosSaiPfcXonLimit[single_asic-xon_4]
testQosSaiHeadroomPoolSize[single_asic]
testQosSaiBufferPoolWatermark[single_asic-wm_buf_pool_lossless]
testQosSaiBufferPoolWatermark[single_asic-wm_buf_pool_lossy]
testQosSaiLossyQueue[single_asic]
testQosSaiDscpQueueMapping[single_asic]
testQosSaiSeparatedDscpQueueMapping[single_asic-downstream]
testQosSaiSeparatedDscpQueueMapping[single_asic-upstream]
testQosSaiDwrr[single_asic]
testQosSaiPgSharedWatermark[single_asic-wm_pg_shared_lossy]
testQosSaiPgHeadroomWatermark[single_asic]
testQosSaiQSharedWatermark[single_asic-wm_q_shared_lossless]
testQosSaiQSharedWatermark[single_asic-wm_q_shared_lossy]
testQosSaiDscpToPgMapping[single_asic]
testQosSaiSeparatedDscpToPgMapping[single_asic-downstream]
testQosSaiSeparatedDscpToPgMapping[single_asic-upstream]
testQosSaiPgSharedWatermark[single_asic-wm_pg_shared_lossless]
testParameter[single_asic]
testQosSaiPfcXoffLimit[single_asic-xoff_1]
testQosSaiPfcXoffLimit[single_asic-xoff_2]
testQosSaiPfcXoffLimit[single_asic-xoff_3]
testQosSaiPfcXoffLimit[single_asic-xoff_4]
testPfcStormWithSharedHeadroomOccupancy[single_asic-xon_1]
testPfcStormWithSharedHeadroomOccupancy[single_asic-xon_2]
testPfcStormWithSharedHeadroomOccupancy[single_asic-xon_3]
testPfcStormWithSharedHeadroomOccupancy[single_asic-xon_4]
testQosSaiPfcXonLimit[single_asic-xon_1]
testQosSaiPfcXonLimit[single_asic-xon_2]
testQosSaiPfcXonLimit[single_asic-xon_3]

Steps to reproduce the issue: 1. 2. 3.

Describe the results you received:

Describe the results you expected:

Additional information you deem important:

**Output of `show version`:**

```
(paste your output here)
```

**Attach debug file `sudo generate_dump`:**

```
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```

[bingwang-ms]

We need to enable this test on t1-64-lag topology because this topology is what we will use on SN4600. Removing the ports from LAG and run the test on the ports is not good enough because there is still a gap.