kernel: move stuff into z_thread_single_abort()

The same code was being copypasted in k_thread_abort()
implementations, just move into z_thread_single_abort().

Signed-off-by: Andrew Boie <andrew.p.boie@intel.com>
diff --git a/arch/arm/core/aarch32/cortex_m/thread_abort.c b/arch/arm/core/aarch32/cortex_m/thread_abort.c
index e2a55da..7c8ccd1 100644
--- a/arch/arm/core/aarch32/cortex_m/thread_abort.c
+++ b/arch/arm/core/aarch32/cortex_m/thread_abort.c
@@ -28,11 +28,7 @@
 
 void z_impl_k_thread_abort(k_tid_t thread)
 {
-	__ASSERT(!(thread->base.user_options & K_ESSENTIAL),
-		 "essential thread aborted");
-
 	z_thread_single_abort(thread);
-	z_thread_monitor_exit(thread);
 
 	if (_current == thread) {
 		if (arch_is_in_isr()) {
diff --git a/arch/posix/core/posix_core.c b/arch/posix/core/posix_core.c
index b44d428..dfb71b5 100644
--- a/arch/posix/core/posix_core.c
+++ b/arch/posix/core/posix_core.c
@@ -493,11 +493,7 @@
 
 	key = irq_lock();
 
-	__ASSERT(!(thread->base.user_options & K_ESSENTIAL),
-		 "essential thread aborted");
-
 	z_thread_single_abort(thread);
-	z_thread_monitor_exit(thread);
 
 	if (_current == thread) {
 		if (tstatus->aborted == 0) { /* LCOV_EXCL_BR_LINE */
diff --git a/kernel/sched.c b/kernel/sched.c
index 28a4964..cdbfa94 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -479,6 +479,9 @@
 
 void z_thread_single_abort(struct k_thread *thread)
 {
+	__ASSERT(!(thread->base.user_options & K_ESSENTIAL),
+		 "essential thread aborted");
+
 	if (thread->fn_abort != NULL) {
 		thread->fn_abort();
 	}
@@ -554,6 +557,7 @@
 	}
 
 	sys_trace_thread_abort(thread);
+	z_thread_monitor_exit(thread);
 }
 
 static void unready_thread(struct k_thread *thread)
diff --git a/kernel/thread_abort.c b/kernel/thread_abort.c
index 65f6f4f..561f0be 100644
--- a/kernel/thread_abort.c
+++ b/kernel/thread_abort.c
@@ -27,11 +27,7 @@
 #if !defined(CONFIG_ARCH_HAS_THREAD_ABORT)
 void z_impl_k_thread_abort(k_tid_t thread)
 {
-	__ASSERT((thread->base.user_options & K_ESSENTIAL) == 0U,
-		 "essential thread aborted");
-
 	z_thread_single_abort(thread);
-	z_thread_monitor_exit(thread);
 
 	/* If we're in an interrupt handler, we reschedule on the way out
 	 * anyway, nothing needs to be done here.