Replace ModuleSpec with Protocols for inputs to MLP

[nschank]

What does this PR do ?

Introduces Protocols for the submodule inputs to MLP and friends.

Associated design doc: Typed ModuleSpec.pdf

I split up the submodule definitions for MLP from TEGroupedMLP because they have totally different APIs.

Note this fixes two bugs with Kitchen:

• feat: m4 leftover changes #2506 broke the use of Kitchen with TEGroupedMLP because pg_collection is now passed instead of tp_group
• Refit prep 3 #2708 broke the use of Kitchen with MLP because stride is now also passed as an argument

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flowchart LR
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        C1[Expert Review] --> C2[Final Review]
    end
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• I have added relevant unit tests
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• I have added proper typing to my code Typing guidelines
• I have added relevant documentation
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[maanug-nv]

/ok to test 51232dd

[yashaswikarnati]

lgtm; thanks for catching few silent bugs in Kitchen layers :). just have some very minor comments

[nschank]

I fixed the lint issues! Also realized I had accidentally used tp instead of expt_tp in Kitchen's grouped layer, so fixed that. Finally, based on Yash's suggestion, I renamed to Grouped... for all the GroupedMLP protocols

[yashaswikarnati]

/ok to test bd154b2

[yaox12]

/ok to test a7582b6