fix: FEVM: signature validation cache for messages with Delegated signatures.

[raulk]

Related Issues

Signature cache entry was constructed with the wrong cache key which did not cover the signature.
Plus, a little bit of gofmt on touched files.

Proposed Changes

Cover the signature by relying on the CID from the SignedMessage, which for the Delegated signature type covers the signature.

Additional Info

Checklist

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[jennijuju]

Add a test plz?

[raulk]

@jennijuju It wouldn't be testing anything useful, just that the key is the CID + signature, which is exactly what the code says, so useless test. Plus, Lotus doesn't already have signature cache unit tests, or does it?

[Stebalien]

This looks like the right way to do it.