sched/sleep: replace all Signal-based sleep implement to Scheduled sleep

Nuttx currently has 2 types of sleep interfaces:

1. Signal-scheduled sleep: nxsig_sleep() / nxsig_usleep() / nxsig_nanosleep()
Weaknesses:
a. Signal-dependent: The signal-scheduled sleep method is bound to the signal framework, while some driver sleep operations do not depend on signals.
b. Timespec conversion: Signal-scheduled sleep involves timespec conversion, which has a significant impact on performance.

2. Busy sleep: up_mdelay() / up_udelay()
Weaknesses:
a. Does not actively trigger scheduling, occupy the CPU loading.

3. New interfaces: Scheduled sleep: nxsched_sleep() / nxsched_usleep() / nxsched_msleep() / nxsched_ticksleep()
Strengths:
a. Does not depend on the signal framework.
b. Tick-based, without additional computational overhead.

Currently, the Nuttx driver framework extensively uses nxsig_* interfaces. However, the driver does not need to rely on signals or timespec conversion.
Therefore, a new set of APIs is added to reduce dependencies on other modules.

(This PR also aims to make signals optional, further reducing the code size of Nuttx.)

Signed-off-by: chao an <anchao.archer@bytedance.com>

wireless/bluetooth/bt_hcicore.c

@@ -1539,7 +1539,7 @@ static void cmd_queue_deinit(void)
 
   while (g_btdev.tx_status == ENOTCONN)
     {
-      nxsig_usleep(1000);
+      nxsched_usleep(1000);
     }
 
   /* Deinitialization */