Farm names should be case-insensitive unique names on chain

[sameh-farouk]

Describe the bug

see: threefoldtech/tfgrid-sdk-ts#1790

Currently we allow same farm name but in a different case to be inserted

tfchain/substrate-node/pallets/pallet-tfgrid/src/farm.rs

Lines 31 to 34 in 36c891c

	ensure!(
	!FarmIdByName::<T>::contains_key(name.clone()),
	Error::<T>::FarmExists
	);

tfchain/substrate-node/pallets/pallet-tfgrid/src/farm.rs

Line 55 in 36c891c

FarmIdByName::<T>::insert(name.to_vec(), id);