Expose more constants for pallet-xcm (#9139)

Let's expose more constants, similar as `AdvertisedXcmVersion`.


![image](https://github.com/user-attachments/assets/5ddc265f-546b-45a0-8235-3f53c3108823)

---------

Co-authored-by: cmd[bot] <41898282+github-actions[bot]@users.noreply.github.com>

Author: bkontur

polkadot/xcm/pallet-xcm/src/lib.rs

@@ -296,6 +296,7 @@ pub mod pallet {
 		type Weigher: WeightBounds<<Self as Config>::RuntimeCall>;
 
 		/// This chain's Universal Location.
+		#[pallet::constant]
 		type UniversalLocation: Get<InteriorLocation>;
 
 		/// The runtime `Origin` type.
@@ -327,9 +328,11 @@ pub mod pallet {
 		type SovereignAccountOf: ConvertLocation<Self::AccountId>;
 
 		/// The maximum number of local XCM locks that a single account may have.
+		#[pallet::constant]
 		type MaxLockers: Get<u32>;
 
 		/// The maximum number of consumers a single remote lock may have.
+		#[pallet::constant]
 		type MaxRemoteLockConsumers: Get<u32>;
 
 		/// The ID type for local consumers of remote locks.

prdoc/pr_9139.prdoc

@@ -0,0 +1,10 @@
+title: Expose more constants for pallet-xcm
+doc:
+- audience:
+  - Runtime Dev
+  - Runtime User
+  description: |-
+    Exposes more constants (UniversalLocation, MaxLockers, MaxRemoteLockConsumers), similar as `AdvertisedXcmVersion`.
+crates:
+- name: pallet-xcm
+  bump: patch