feat: Gate-keeping validator set from validators without required public keys

[hacheigriega]

Motivation

Once a proving scheme is enabled, we want to gate-keep the validator store to ensure that all validators in the store have the required public key. Also, since an account cannot register a public key before registering itself as a validator, the CreateValidator has to handle registration of the required public keys.

Explanation of Changes

We wrap the staking module's message server to replace the original CreateValidator handler with the new CreateSEDAValidator handler. A few things to note about the new handler:

• It checks if the secp256k1 proving scheme has been activated and, if it has, requires the secp256k1 public key to be present in the transaction message.
• The transaction command tx staking create-validator remains the same.
• A flag --without-seda-keys can be added to skip generating and uploading the SEDA keys.

The gentx has also been updated to generate and upload the SEDA keys.

Testing

We first set up a local network with a single genesis validator and, before the proving scheme activation period is over, create a few new validators with the --without-seda-keys flag to make the public key registration rate fall below the threshold. This cancels the activation process. Subsequently, the new validators send the tx pubkey add-seda-keys to generate and upload the required public keys. This again starts the activation process and eventually activates the proving scheme with the guarantee that all validators have registered their public keys.

Related PRs and Issues

Related: #422 (to close the issue, we still need to update the unjail logic - addressed in #434)

[hacheigriega]

With the commit 2b64145 the original SDK handlers should work as before. The SDK's CreateValidator, however, is discarded in favor of SEDA Chain's CreateSEDAValidator. Cc @Thomasvdam

[Thomasvdam]

We should also remember to update the docs for creating a validator once we go to testnet and mainnet. :D