Leniently accept tasks after context close in lifecycle stop phase

Schedulers remain strict, just plain executors are lenient on shutdown now.
An early shutdown for executors can be enforced via setStrictEarlyShutdown.

Closes gh-32226

spring-core/src/main/java/org/springframework/core/task/SimpleAsyncTaskExecutor.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2023 the original author or authors.
+ * Copyright 2002-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -165,13 +165,16 @@ public class SimpleAsyncTaskExecutor extends CustomizableThreadCreator
 	}
 
 	/**
-	 * Specify a timeout for task termination when closing this executor.
-	 * The default is 0, not waiting for task termination at all.
+	 * Specify a timeout (in milliseconds) for task termination when closing
+	 * this executor. The default is 0, not waiting for task termination at all.
 	 * <p>Note that a concrete >0 timeout specified here will lead to the
 	 * wrapping of every submitted task into a task-tracking runnable which
 	 * involves considerable overhead in case of a high number of tasks.
 	 * However, for a modest level of submissions with longer-running
 	 * tasks, this is feasible in order to arrive at a graceful shutdown.
+	 * <p>Note that {@code SimpleAsyncTaskExecutor} does not participate in
+	 * a coordinated lifecycle stop but rather just awaits task termination
+	 * on {@link #close()}.
 	 * @param timeout the timeout in milliseconds
 	 * @since 6.1
 	 * @see #close()
@@ -183,18 +186,6 @@ public class SimpleAsyncTaskExecutor extends CustomizableThreadCreator
 		this.activeThreads = (timeout > 0 ? Collections.newSetFromMap(new ConcurrentHashMap<>()) : null);
 	}
 
-	/**
-	 * Return whether this executor is still active, i.e. not closed yet,
-	 * and therefore accepts further task submissions. Otherwise, it is
-	 * either in the task termination phase or entirely shut down already.
-	 * @since 6.1
-	 * @see #setTaskTerminationTimeout
-	 * @see #close()
-	 */
-	public boolean isActive() {
-		return this.active;
-	}
-
 	/**
 	 * Set the maximum number of parallel task executions allowed.
 	 * The default of -1 indicates no concurrency limit at all.
@@ -224,6 +215,18 @@ public class SimpleAsyncTaskExecutor extends CustomizableThreadCreator
 		return this.concurrencyThrottle.isThrottleActive();
 	}
 
+	/**
+	 * Return whether this executor is still active, i.e. not closed yet,
+	 * and therefore accepts further task submissions. Otherwise, it is
+	 * either in the task termination phase or entirely shut down already.
+	 * @since 6.1
+	 * @see #setTaskTerminationTimeout
+	 * @see #close()
+	 */
+	public boolean isActive() {
+		return this.active;
+	}
+
 
 	/**
 	 * Executes the given task, within a concurrency throttle