chore: Move eth functions out of api

[geoff-vball]

Related Issues

Closes #9825

Leaving bigger changes from #9870 to another day.

Proposed Changes

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[arajasek]

2 suggestions:

• move the new types to a new chain/types/eth/ directory?
• can EthTxReceipt stay in api? I don't think we need to move it.

I'm not thrilled about the JSON marshaling stuff moving into chain/types, but the alternative is to have type aliases in the API module that we define the JSON logic on. I don't think we need to do that now (but would like it to happen someday -- maybe open an issue for it?)