## Proposed Changes
This is an extraction of the quoted int code from #1569, that I've come to rely on for #1544.
It allows us to parse integers from serde strings in YAML, JSON, etc. The main differences from the code in Paul's original PR are:
* Added a submodule that makes quoting mandatory (`require_quotes`).
* Decoding is generic over the type `T` being decoded. You can use `#[serde(with = "serde_utils::quoted_u64::require_quotes")]` on `Epoch` and `Slot` fields (this is what I do in my slashing protection PR).
I've turned on quoting for `Epoch` and `Slot` in this PR, but will leave the other `types` changes to you Paul.
I opted to put everything in the `conseus/serde_utils` module so that BLS can use it without a circular dependency. In future when we want to publish `types` I think we could publish `serde_utils` as `lighthouse_serde_utils` or something. Open to other ideas on this front too.
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