Add a governor extension that implements a security council

[Amxx]

Fixes #5301

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[Amxx]

To do when #5290 is merged:

Suggested change

	uint256 proposalId = hashProposal(targets, values, calldatas, descriptionHash);
	uint256 proposalId = getProposalId(targets, values, calldatas, descriptionHash);

[arr00]

#5301

[arr00]

Looks good other than some comments. Would it make sense to call it something like GovernorCancelCouncil to be more explicit? I could imagine daos having multiple different "security" related councils.

[arr00]

Compound Governance already has a feature like this where the council is called the proposalGuardian. If we aren't too against the wording we could reuse it.

https://github.com/compound-finance/compound-governance/blob/15614c913d548c7a7a4a3f3543069562d120eb7d/contracts/GovernorBravoDelegate.sol#L768-L784