Update Sufficient Asset Minimum Balances

Update: Recommend rejecting this proposal. I will make a new one to go with the Asset Hub upgrade that actually updates the Existential Deposit. See this PR for more details.

This referendum is related to the reduction of existential deposit on Asset Hubs.

When you pay fees in sufficient assets, the system still calculates the base transaction fee in DOT. It converts it to the asset fee amount using the ratio of minimum balances. So:

fee_in_dot * asset_min_balance / dot_existential_deposit

So, if you reduce the DOT ED by a factor of 10, you also increase fees in sufficient assets by a factor of 10 (Asset Conversion, coming soon, to avoid all this).

This proposal reduces the minimum balance requirement for all sufficient assets (USDT, USDC, and KSM) by a factor of 10, preserving the ratio. There is also a fourth call to update the metadata for bridged KSM, since that failed when creating the asset due to the SafeCallFilter.