Adds new move_stake_limit extrinsic

[mcjkula]

Description

Adds new move_stake_limit extrinsic.

Related Issue(s)

• Closes #[issue number]

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Other (please describe):

Breaking Change

If this PR introduces a breaking change, please provide a detailed description of the impact and the migration path for existing applications.

Checklist

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have run cargo fmt and cargo clippy to ensure my code is formatted and linted correctly
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

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Additional Notes

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[mcjkula]

I would hope someone can look through my code, test if everything works and help with the PR. Would highly appreciate it!

[open-junius]

pls check this one https://github.com/opentensor/subtensor/blob/main/pallets/subtensor/src/macros/dispatches.rs#L1869. looks like it is already implemented.

[mcjkula]

swapStake and moveStake are different though, because with swapStake you can only move from subnet to subnet with the same cold- and hotkey, while moveStake allows you to move from subnet to subnet with any hotkey (or just move stake from hotkey to hotkey in the same subnet). @open-junius

Depending on how you would handle such case it would make sense to either change moveStake to only allow changing between hotkeys in the same subnet, or remove swapStake as its just a subset of what moveStake does. (or we let them both co-exist as they are)