[Core][VLM] Test registration for OOT multimodal models

[ywang96]

This PR formally the support for OOT multimodal model registration. This was enabled alongside automatic detection of multimodal models in #7168, but has yet to be properly tested and documented.

FIX #8667

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[youkaichao]

can you add some tests?

[ywang96]

can you add some tests?

Yea, I made this PR so that the person who reported the issue can use it to test if it's working for him to unblock him

[ywang96]

There's some issue with the ordering of when is_multimodal_model needs to be called and when the model actually gets registered to vLLM...I'm still investigating.

[ywang96]

This PR should be working now. I have verified test_oot_registration.py passed locally in my environment.

[ywang96]

@DarkLight1337 Turned out switching the order solved the issue...I'm honestly not sure why though :/

52b600b seems to show that CUDA initialization in any of the plugins will interfere with vLLM's memory allocation even when the plugin isn't being used. This isn't good...

Yep...

[DarkLight1337]

@youkaichao any idea about this?

[youkaichao]

sorry I missed the context here. can you summarize the current status? DM is also fine.

[ywang96]

sorry I missed the context here. can you summarize the current status? DM is also fine.

Yea I shared with you on slack - I think it actually has nothing to do with CUDA re-init

[DarkLight1337]

Please don't merge this yet - we still need to investigate how installing the plugin is causing the test to fail.

[DarkLight1337]

I've added an option to lazy import the registered models based on #9000, see if this fixes the problem.

[DarkLight1337]

Alright, tests pass now. @youkaichao feel free to merge if you are ok with the latest changes.