[WIP] Add AST Adapter

[dylanberens]

map HF ASTConfig to HookedTransformerConfig

build custom ASTEmbed w/ 16x16 Conv2d patch extraction

translate q/k/v_proj and fc1/fc2 dense weights to TL standard blocks

implement CLS and Distillation token averaging for AST MLP head

apply dual layernorm architecture to pooled tokens

draft local matrix parity test suite (current max diff: ~0.05)

Description

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Fixes # (issue)

Type of change

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• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

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Checklist:

• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• 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 have not rewritten tests relating to key interfaces which would affect backward compatibility