Make SSH session generator support generating session files for all devices, like fanout switches.

[r12f]

Description of PR

Summary:
Currently, the SSH repo generator will only generate the session files for DUT and PTF in testbeds, but not all the other devices, such as fanout switches and servers.

This change is to add this support in it.

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?

Currently, the SSH repo generator will only generate the session files for DUT and PTF in testbeds, but not all the other devices, such as fanout switches and servers.

How did you do it?

This change updates the ssh_session_gen.py to parse the device inventory csv files, so we can generate all sessions for it.

How did you verify/test it?

Run it locally, and it outputs the session files as below. Besides the testbeds, now we also outputs the devices folder:

Any platform specific information?

No.

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

N/A.

Documentation

No changes on how to use it. N/A.

[mssonicbld]

The pre-commit check detected issues in the files touched by this pull request.
The pre-commit check is a mandatory check, please fix detected issues.

Detailed pre-commit check results:
trim trailing whitespace.................................................Failed
- hook id: trailing-whitespace
- exit code: 1
- files were modified by this hook

Fixing ansible/devutil/device_inventory.py
Fixing ansible/ssh_session_gen.py

fix end of files.........................................................Failed
- hook id: end-of-file-fixer
- exit code: 1
- files were modified by this hook

Fixing ansible/devutil/device_inventory.py

check yaml...........................................(no files to check)Skipped
check for added large files..............................................Passed
check python ast.........................................................Passed
flake8...................................................................Failed
- hook id: flake8
...
[truncated extra lines, please run pre-commit locally to view full check results]

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