Enhance smart contract's seed security

[samuelmanzanera]

Is your feature request related to a problem?

Archethic's smart contract leverages secret delegation to allow self-triggered transactions.
In this context, the smart contract's owner encrypts the chain's seed with the storage nonce public key (known by all the nodes).

Of course, to restrict the impact of the seed's usage, the inherit constraints define a whitelist of mutated properties allowed by the nodes.
So, a node could not change something which was not expected.

Because the storage nonce is known by all the nodes at any time, some people could have access to all the seeds of the smart contracts and try to leverage this to build transactions unexpected.

To prevent security issue, if the inherit constraints were not well scoped, we can increase the way the transactions are triggered to target only authorized nodes and leverage proof of work to ensure the origin.

Describe the solution you'd like

To tackle this problem, I propose to ensure the origin of the transactions by changing the Contracts.accept_new_contract/3 function to check the origin signature based on the list of authorized nodes

Additional context

Epic: #608

[samuelmanzanera]

No need after #945