Create CLI tool to help with mainnet export testing

[MSalopek]

Problem

At the time of writing, we are using an approach that involves running gaiad export, then manipulating the genesis.json to inject a validator set that we use to run a localnet with production data.

The main drawback of this approach are:

• export is cumbersome due to time it takes to export and tinker
• sometimes the export fails due to resource constraints (possible leaks in the export code)

Closing criteria

A command is added or a new binary is created that should be used only in testing. The binary should be able to make changes to the local mainnet node and make it suitable for local testing.

The changes include (but are not limited to):

• injecting a new validator set
• removing the old validator set
• injecting addresses that can be used in testing (while not affecting existing addresses)

The exact CLI cmd can be defined later, it is more important to test out the approach outlined here:

• https://github.com/cosmos/cosmos-sdk/blob/main/docs/build/building-apps/05-app-testnet.md#required-changes