Move minimum required pigeon version from hard-coded to governance

[maharifu]

Related Github tickets

• Move minimum required pigeon version from hard-coded to governance VolumeFi/paloma#1640

Background

At the moment, we store the minimum required version of Pigeon as hard-coded const inside Paloma. This means to enforce a Pigeon update, we need to roll-out a new version of the protocol as well, which often creates unnecessary noise and maintenance overhead.

Instead, this information should live on the chain directly, and be addressable via governance vote.

• Generalize the restriction to pigeon requirements, so we can add new restriction in the future, instead of only minimum version
• Add pigeon requirements to valset keeper, as the valset module is the one requiring this information
• Add scheduled pigeon requirements, so we can schedule rollouts to a specific block height
• Add new gRPC query - q valset get-pigeon-requirements - to get current and scheduled requirements
• Add new tx - tx gov submit-legacy-proposal valset propose-pigeon-requirements - to propose changes to pigeon requirements
• The valset module checks for pending scheduled changes at each BeginBlock. When a change is applied, scheduled changes are cleared
• Added this information to genesis

Testing completed

• test coverage exists or has been added/updated
• tested in a private testnet

Breaking changes

• I have checked my code for breaking changes
• If there are breaking changes, there is a supporting migration.

[byte-bandit]

Good stuff. 2 small remarks

[byte-bandit]

Nice work!