[arm64] add hw thread self (#8942)

* [libcpu] arm64: Add hardware thread_self support

This patch introduces hardware-based thread self-identification
for the AArch64 architecture. It optimizes thread management by
using hardware registers to store and access the current thread's
pointer, reducing overhead and improving overall performance.

Changes include:
- Added `ARCH_USING_HW_THREAD_SELF` configuration option.
- Modified `rtdef.h`, `rtsched.h` to conditionally include
  `critical_switch_flag` based on the new config.
- Updated context management in `context_gcc.S`, `cpuport.h`
  to support hardware-based thread self.
- Enhanced `scheduler_mp.c` and `thread.c` to leverage the new
  hardware thread self feature.

These modifications ensure better scheduling and thread handling,
particularly in multi-core environments, by minimizing the
software overhead associated with thread management.

Signed-off-by: Shell <smokewood@qq.com>

* fixup: address suggestion

* fixup: rt_current_thread as global

* scheduler: add cpu object for UP scheduler

Also, maintain the rt_current_thread in cpu object on UP scheduler.

---------

Signed-off-by: Shell <smokewood@qq.com>

include/rtdef.h

@@ -740,8 +740,10 @@ struct rt_cpu
         struct rt_thread        *current_thread;
 
         rt_uint8_t              irq_switch_flag:1;
-        rt_uint8_t              critical_switch_flag:1;
         rt_uint8_t              sched_lock_flag:1;
+#ifndef ARCH_USING_HW_THREAD_SELF
+        rt_uint8_t              critical_switch_flag:1;
+#endif /* ARCH_USING_HW_THREAD_SELF */
 
         rt_uint8_t              current_priority;
         rt_list_t               priority_table[RT_THREAD_PRIORITY_MAX];
@@ -763,10 +765,19 @@ struct rt_cpu
     struct rt_cpu_usage_stats   cpu_stat;
 #endif
 };
-typedef struct rt_cpu *rt_cpu_t;
+
+#else /* !RT_USING_SMP */
+struct rt_cpu
+{
+    struct rt_thread            *current_thread;
+};
 
 #endif /* RT_USING_SMP */
 
+typedef struct rt_cpu *rt_cpu_t;
+/* Noted: As API to reject writing to this variable from application codes */
+#define rt_current_thread rt_thread_self()
+
 struct rt_thread;
 
 #ifdef RT_USING_SMART