Only sudo can set the swap fee rate

[gztensor]

We are limiting the capability to set fee rates. Subnet owners will no longer be able to set them.

Acceptance criteria:

• Subnet owner (Charlie) cannot set the fee rate (sends swap::setFeeRate(netuid = 4, fee_rate = 123) extrinsic, receives Bad Origin error)
• Random address (Alice) cannot set the fee rate (sends swap::setFeeRate(netuid = 4, fee_rate = 123) extrinsic, receives Bad Origin error)
• Sudo can set fee rate from 0 to 10000 (sends sudo::swap::setFeeRate(netuid = 4, fee_rate = 123) extrinsic)
• Sudo cannot set fee rate if value is invalid (10001) (sends sudo::swap::setFeeRate(netuid = 4, fee_rate = 10001) extrinsic, receives FeeRateTooHigh error)

Tested on devnet with Apps UI.