Nomination pool configurations can be managed by custom origin (#3959)

closes https://github.com/paritytech/polkadot-sdk/issues/3894

Allows Nomination Pool configuration to be set by a custom origin
instead of root.

In runtimes, we would set this to be `StakingAdmin`, same as for
pallet-staking.

---------

Co-authored-by: Liam Aharon <liam.aharon@hotmail.com>

substrate/frame/nomination-pools/src/mock.rs

@@ -17,8 +17,11 @@
 
 use super::*;
 use crate::{self as pools};
-use frame_support::{assert_ok, derive_impl, parameter_types, traits::fungible::Mutate, PalletId};
-use frame_system::RawOrigin;
+use frame_support::{
+	assert_ok, derive_impl, ord_parameter_types, parameter_types, traits::fungible::Mutate,
+	PalletId,
+};
+use frame_system::{EnsureSignedBy, RawOrigin};
 use sp_runtime::{BuildStorage, FixedU128};
 use sp_staking::{OnStakingUpdate, Stake};
 
@@ -289,6 +292,11 @@ parameter_types! {
 	pub static CheckLevel: u8 = 255;
 	pub const PoolsPalletId: PalletId = PalletId(*b"py/nopls");
 }
+
+ord_parameter_types! {
+	pub const Admin: u128 = 42;
+}
+
 impl pools::Config for Runtime {
 	type RuntimeEvent = RuntimeEvent;
 	type WeightInfo = ();
@@ -303,6 +311,7 @@ impl pools::Config for Runtime {
 	type MaxMetadataLen = MaxMetadataLen;
 	type MaxUnbonding = MaxUnbonding;
 	type MaxPointsToBalance = frame_support::traits::ConstU8<10>;
+	type AdminOrigin = EnsureSignedBy<Admin, AccountId>;
 }
 
 type Block = frame_system::mocking::MockBlock<Runtime>;