feat(protocol): allow local.params.parentMetaHash to remain as 0

[dantaik]

Previously if this parameter is zero, we set it to parent's hash, now we simply use 0. This will avoid a SLOAD for many blocks.

@davidtaikocha @smtmfft will this be a breaking change for client or prover? Note now the metadata may have parentMetaHash as 0.

[openzeppelin-code]

feat(protocol): allow local.params.parentMetaHash to remain as 0

Generated at commit: 76953e243a5303b954d0223c53a47db0af35ea3e

🚨 Report Summary

	Severity Level	Results
Contracts	Critical High Medium Low Note Total	3 3 0 7 42 55
Dependencies	Critical High Medium Low Note Total	0 0 0 0 0 0

---

For more details view the full report in OpenZeppelin Code Inspector

[davidtaikocha]

Don't think its a break change for client, but might break zk cc @smtmfft

[smtmfft]

we get parentMeta from blockpropose event, should be the same I think