fix(stable2512): adapt EnableAsyncBackingAndCoretime migration to stable2512 scheduler

After merging upgrade/1.12.0-all, the free-stuck-AvailabilityCores code from
PR #29 doesn't compile on stable2512 — the upstream paritytech#4937 rewrite removed
`AvailabilityCores` + `CoreOccupied` storage from `pallet_scheduler`. Only
`ClaimQueue` survives, now storing `VecDeque<Assignment>` instead of
`VecDeque<ParasEntryType<T>>`.

On stable2512 the stuck-core scenario doesn't manifest either: paritytech#4937 fixes the
fragment-chain fork deadlock natively, so candidates always reach availability
under the normal flow. We still kill `ClaimQueue` in the migration so the
scheduler rebuilds from the just-updated `ActiveConfig`.

Also dedupes `scale-type-resolver` from Cargo.lock (duplicate entry introduced
by the merge).

Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>

Author: DrudgeRajen

Cargo.lock

@@ -2437,37 +2437,22 @@ pub mod migrations {
 				cfg.node_features.set(3, true);
 			});
 
-			// Force-free any stuck AvailabilityCores. In normal flow cores transition
-			// Paras(entry) → Free via ParaInherent bitfield signaling availability complete;
-			// but when the config just changed under an occupied core (e.g. async-backing
-			// enabled while a v1.12.0-pre-#4937 relay has a capacity=2 cumulus collator
-			// producing forks), the occupying entry never concludes. Until session rotation
-			// the core stays stuck. Session rotation calls `push_occupied_cores_to_assignment_provider`
-			// which replaces every Paras(_) with Free. We do the same here so the next
-			// ParaInherent pass can schedule fresh candidates atomically with setCode.
-			//
-			// Caveat: relay-client subsystems cache fragment-chain / SessionInfo per session
-			// in Rust memory. Even after freeing storage, those caches persist until the
-			// next real session boundary OR validator-process restart. Operator action
-			// required: `kubectl rollout restart deploy/validator-*` after setCode.
-			parachains_scheduler::AvailabilityCores::<Runtime>::mutate(|cores| {
-				for core in cores.iter_mut() {
-					*core = parachains_scheduler::CoreOccupied::Free;
-				}
-			});
-			// Drop stale claims too — next block's free_cores_and_fill_claimqueue
-			// repopulates from AssignmentProvider.
+			// Drop stale claim queue so the scheduler rebuilds from fresh config
+			// on the next block. stable2512 has #4937 natively so there is no
+			// stuck-AvailabilityCores scenario — only ClaimQueue needs clearing.
+			// (v1.12.0 variant of this migration also freed AvailabilityCores;
+			// that storage no longer exists in stable2512 after the #4937 rework.)
 			parachains_scheduler::ClaimQueue::<Runtime>::kill();
 
 			log::info!(
 				target: "runtime",
 				"EnableAsyncBackingAndCoretime: num_cores={}, max_vals_per_core=None, \
 				 lookahead=1, async_backing=(depth=1, ancestry=2), node_features[0,1,3]=true, \
-				 AvailabilityCores freed, ClaimQueue cleared",
+				 ClaimQueue cleared",
 				num_cores,
 			);
 
-			<Runtime as frame_system::Config>::DbWeight::get().reads_writes(2, 3)
+			<Runtime as frame_system::Config>::DbWeight::get().reads_writes(1, 2)
 		}
 	}