Fix #3825: handle hoisted-local cleanup before combined-tokens disposal

For an async iterator with an [EnumeratorCancellation] cancellation token, the
hoisted-local cleanup (stfld <>u__N(this, null)) can be emitted before the
combined CancellationTokenSource disposal in the set-result and catch blocks.
CheckSetResultReturnBlock and ValidateCatchBlock only consumed that cleanup after
the disposal, so the `pos + 2 == count` test missed the dispose pattern and the
analysis failed, leaving the raw state machine (catch (object), goto case, ...).

Allow the cleanup to appear before the combined-tokens disposal as well.

Assisted-by: Copilot:claude-opus-4.8:GitHub Copilot CLI

ICSharpCode.Decompiler.Tests/TestCases/Pretty/AsyncStreams.cs

@@ -71,6 +71,20 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
 				await Task.Delay(10).ConfigureAwait(continueOnCapturedContext: false);
 			}
 		}
+
+		public static async IAsyncEnumerable<int> AwaitInFinallyWithCancellation([EnumeratorCancellation] CancellationToken cancellationToken)
+		{
+			await Task.Yield();
+			try
+			{
+				yield return 1;
+				await Task.Delay(10, cancellationToken);
+			}
+			finally
+			{
+				await Task.Yield();
+			}
+		}
 	}
 
 	public struct TestStruct

ICSharpCode.Decompiler/IL/ControlFlow/AsyncAwaitDecompiler.cs

@@ -911,6 +911,11 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 			finalStateKnown = true;
 			pos++;
 
+			// [optional] stfld <>u__N(ldloc this, ldnull)
+			// The hoisted-local cleanup may appear either before or after the combined-tokens disposal
+			// (the latter is present for async iterators with an [EnumeratorCancellation] token).
+			MatchHoistedLocalCleanup(block, ref pos);
+
 			if (pos + 2 == block.Instructions.Count && block.MatchIfAtEndOfBlock(out var condition, out var trueInst, out var falseInst))
 			{
 				if (MatchDisposeCombinedTokens(blockContainer, condition, trueInst, falseInst, blocksAnalyzed, out var setResultAndExitBlock))
@@ -1088,6 +1093,12 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 				finalState = newState;
 				finalStateKnown = true;
 			}
+
+			// [optional] stfld <>u__N(ldloc this, ldnull)
+			// The hoisted-local cleanup may appear either before or after the combined-tokens disposal
+			// (the latter is present for async iterators with an [EnumeratorCancellation] token).
+			MatchHoistedLocalCleanup(catchBlock, ref pos);
+
 			if (pos + 2 == catchBlock.Instructions.Count && catchBlock.MatchIfAtEndOfBlock(out var condition, out var trueInst, out var falseInst))
 			{
 				if (MatchDisposeCombinedTokens(handlerContainer, condition, trueInst, falseInst, blocksAnalyzed, out var setResultAndExitBlock))