Ensure type-checker understands use of Submodules in llava_model

[nschank]

What does this PR do ?

In order to safely refactor Submodules classes, I want to make sure I can easily find everywhere those classes are being referenced. This updates llava_model to appropriately type-check the submodules its introspecting into, which ensures the type-checker (and things like Find References in VSCode) will understand the usage of these objects below.

Relevant design doc: https://docs.google.com/document/d/1shyv0iKEzRdevLOlouF_NktbdJazvWifqxUwPXFigQE/edit?tab=t.0#heading=h.uwes2zo47yg6

Split out from #2834

Contribution process

flowchart LR
    A[Pre-checks] --> B[PR Tests]
    subgraph Code Review/Approval
        C1[Expert Review] --> C2[Final Review]
    end
    B --> C1
    C2 --> D[Merge]

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Pre-checks

• I want this PR in a versioned release and have added the appropriate Milestone (e.g., Core 0.8)
• I have added relevant unit tests
• I have added relevant functional tests
• I have added proper typing to my code Typing guidelines
• I have added relevant documentation
• I have run the autoformatter.sh on my PR

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[yashaswikarnati]

/ok to test c23839a

[yashaswikarnati]

/ok to test 8bcc0b8

[chtruong814]

/ok to test 35920f8