Bypass Signature Validity Check

Submitted by (3) cryptphi, also found by 0x1f8b and defsec

Summary:

https://code4rena.com/reports/2022-08-rigor/#m-03-signature-checks-could-be-passed-when-signaturedecoderrecoverkey-returns-0

It is possible to pass Signature Validity check with an SignatureDecoder.recoverKey() returns 0 whenever the builder and /or contractor have an existing approved hash for a data.

Mitigation:

There should be a require check for _recoveredSignature != 0 in checkSignatureValidity().