Chore cargo docs

[Autoparallel]

Purpose

Clean up arbiter-core and Cargo docs.

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Tasks Completed

• Added Cargo docs to each module inside of arbiter-core except for bindings. We should consider adding documentation there, but make sure we prevent overwrites in some way.
• Merged in a removal of any and all agents and had this reflected in the documentation.
• Fixed any bugs or missing implementations with custom errors, and made their names more idiomatic (i.e., removed Error from the enum variants.
• Had all of the revm logs cast into ethers logs done in middleware module and made revm_logs_to_ethers_logs() private.
• Reduced visibility of a handful of structs, enums, and functions/methods.

[0xJepsen]

This all looks really clean to me! We got to remember to add the link for the other docs later