Test AN/LT behavior

[lguohan]

Description

Steps to reproduce the issue:

1. Enable the autoneg, but fec override with None.
2. Need steps to configure the fanout to simulate the behavior.

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`:**

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

[Blueve]

Someone added LT related CLI recently, however our CLI document are not up to date: sonic-net/sonic-utilities#2071

What is the expected behavior? status changed to from "not_trained" to "trained" after speed AN completed?

Update:
Feature owner raised CLI doc PR: https://github.com/Azure/sonic-utilities/pull/2257/files

[yxieca]

@prgeor can you help clarify?

[prgeor]

Someone added LT related CLI recently, however our CLI document are not up to date: sonic-net/sonic-utilities#2071

What is the expected behavior? status changed to from "not_trained" to "trained" after speed AN completed?

Update: Feature owner raised CLI doc PR: https://github.com/Azure/sonic-utilities/pull/2257/files

@Blueve @yxieca link training status can be the following as per this HLD

[kamalsahu0001]

@prgeor .... In order to test this test gap, is there any specific vendor cables that we have to test? and all type of cables that we have to test.

[prgeor]

@kamalsahu0001 100G DAC is sufficient

[StormLiangMS]

hi @prgeor this one seems a platform related test gap, assigned to you for further triage.