feat: add testnetify logic

[czarcas7ic]

Description

Closes: #XXXX

This PR adds the required logic for creating a testnet from mainnet state. This PR will be upstreamed to the SDK as soon as we merge it here, and plug in the required logic to the osmosis repo.

Author Checklist

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I have...

• [ ] included the correct type prefix in the PR title
• [ ] added ! to the type prefix if API or client breaking change
• [ ] targeted the correct branch (see PR Targeting)
• [ ] provided a link to the relevant issue or specification
• [ ] followed the guidelines for building modules
• [ ] included the necessary unit and integration tests
• [ ] added a changelog entry to CHANGELOG.md
• [ ] included comments for documenting Go code
• [ ] updated the relevant documentation or specification
• [ ] reviewed "Files changed" and left comments if necessary
• [ ] confirmed all CI checks have passed

Reviewers Checklist

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I have...

• [ ] confirmed the correct type prefix in the PR title
• [ ] confirmed ! in the type prefix if API or client breaking change
• [ ] confirmed all author checklist items have been addressed
• [ ] reviewed state machine logic
• [ ] reviewed API design and naming
• [ ] reviewed documentation is accurate
• [ ] reviewed tests and test coverage
• [ ] manually tested (if applicable)