Write consumer IBC app

[tbruyelle]

• gno version of https://github.com/allinbits/vaas/tree/main/x/vaas/consumer
• IBC v2 compatible
• should be able to update the validator set (similarly to feat: utilize params keeper for valset updates gnolang/gno#3999)
• check if there is friction with feat(validators): limit valset changes gnolang/gno#4834