Add additional argument to `unstake_all` and `unstake_all` (or `remove_all`)

[basfroman]

Issue: Inaccurate "Unstake All" Behavior in Dynamic Environments

We've observed that when users try to unstake their entire Alpha from a hotkey, a small residual stake sometimes remains. This happens because emissions accrue between the time the client queries the stake amount and when the unstake transaction executes. While we've implemented SDK-side adjustments, a truly robust solution requires chain-level changes.

We propose adding arguments to the remove_stake and remove_stake_limit functions in Subtensor. This would allow the chain to precisely understand the user's intent to unstake all Alpha, ensuring complete and accurate withdrawals even in dynamic network conditions.

Please read more about the issue from SDK side here.