Deprecate xcm::body::TREASURER_INDEX constant, use standard Treasury varian instead (#3608)

Deprecate the `xcm::body::TREASURER_INDEX` constant and use the standard
Treasury variant from the `xcm::BodyId` type instead.

To align with the production runtimes:
https://github.com/polkadot-fellows/runtimes/pull/149

cumulus/parachains/runtimes/collectives/collectives-westend/src/xcm_config.rs

@@ -59,7 +59,7 @@ parameter_types! {
 	pub const GovernanceLocation: Location = Location::parent();
 	pub const FellowshipAdminBodyId: BodyId = BodyId::Index(xcm_constants::body::FELLOWSHIP_ADMIN_INDEX);
 	pub AssetHub: Location = (Parent, Parachain(1000)).into();
-	pub const TreasurerBodyId: BodyId = BodyId::Index(xcm_constants::body::TREASURER_INDEX);
+	pub const TreasurerBodyId: BodyId = BodyId::Treasury;
 	pub AssetHubUsdtId: AssetId = (PalletInstance(50), GeneralIndex(1984)).into();
 	pub UsdtAssetHub: LocatableAssetId = LocatableAssetId {
 		location: AssetHub::get(),

polkadot/runtime/westend/constants/src/lib.rs

@@ -130,6 +130,8 @@ pub mod xcm {
 		const ROOT_INDEX: u32 = 0;
 		// The bodies corresponding to the Polkadot OpenGov Origins.
 		pub const FELLOWSHIP_ADMIN_INDEX: u32 = 1;
+		#[deprecated = "Will be removed after August 2024; Use `xcm::latest::BodyId::Treasury` \
+			instead"]
 		pub const TREASURER_INDEX: u32 = 2;
 	}
 }

polkadot/runtime/westend/src/xcm_config.rs

@@ -34,9 +34,7 @@ use runtime_common::{
 };
 use sp_core::ConstU32;
 use westend_runtime_constants::{
-	currency::CENTS,
-	system_parachain::*,
-	xcm::body::{FELLOWSHIP_ADMIN_INDEX, TREASURER_INDEX},
+	currency::CENTS, system_parachain::*, xcm::body::FELLOWSHIP_ADMIN_INDEX,
 };
 use xcm::latest::prelude::*;
 use xcm_builder::{
@@ -231,7 +229,7 @@ parameter_types! {
 	// FellowshipAdmin pluralistic body.
 	pub const FellowshipAdminBodyId: BodyId = BodyId::Index(FELLOWSHIP_ADMIN_INDEX);
 	// `Treasurer` pluralistic body.
-	pub const TreasurerBodyId: BodyId = BodyId::Index(TREASURER_INDEX);
+	pub const TreasurerBodyId: BodyId = BodyId::Treasury;
 }
 
 /// Type to convert the `GeneralAdmin` origin to a Plurality `Location` value.