Create API to get the genesis node shared public key

[samuelmanzanera]

Is your feature request related to a problem?

Currently, we have an API to get the storage nonce public key, however this data is not immutable. If someday we wish to change the nonce to distribute the shards due to some issue or security matters, all the smart contract would not be to be executed.

But using the first key of the node_shared_keys which is known by all the authorized_nodes we can ensure this information will not change.

Describe the solution you'd like

We should then expose an API that clients (wallet, SDKs, Playgrounds, etc..) have to use to encrypt the chain's seed with the node's shared key.

Additional context

No response

Epic

No response