Add __del__ at Vllm for deleting model

[vkehfdl1]

Description

When using more than one Vllm model in single program, it occurs error. There is a vllm function destroy_model_parallel() for preventing this kind of error.

There is a description about this issue at here.

I tested use two Vllm instance in a single python file at CUDA environment. And it did great.
Without this code, it occurred error 'data parallel group is already initialized.'

Fixes # (issue)

Type of Change

Please delete options that are not relevant.

Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

• I stared at the code and made sure it makes sense
• Plus, I tested it in my H100 instance with CUDA, and it worked well when I make two Vllm instance and run it.

Suggested Checklist:

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added Google Colab support for the newly added notebooks.
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I ran make format; make lint to appease the lint gods

[hatianzhang]

thanks @vkehfdl1 lgtm!

[logan-markewich]

@vkehfdl1 apologies, with v0.10.0 the project structure has changed slightly

I can take a stab at porting this PR in a bit, if you don't get to it first :)

[hatianzhang]

address refactoring here #10733