!sched/clock: remove CONFIG_SYSTEM_TIME64 and always use 64-bit time

The 32-bit system clock has a limited range (~497 days) and the
configuration knob is no longer worth the complexity given that
practically every modern target already enables it.  Make 64-bit
time_t/clock_t/sclock_t/nuttx_time_t the only supported flavor.

Specifically:
  - Drop the SYSTEM_TIME64 Kconfig option and its dependent
    PERF_OVERFLOW_CORRECTION/HRTIMER guards in sched/Kconfig.
  - Remove every #ifdef CONFIG_SYSTEM_TIME64 branch in headers
    (include/{sys/types.h,limits.h,inttypes.h,nuttx/clock.h,
    nuttx/fs/hostfs.h}) and core code paths
    (sched/clock/clock.h, drivers/power/pm/pm_procfs.c,
    drivers/rpmsg/rpmsg_ping.c, fs/procfs/fs_procfsuptime.c,
    libs/libc/wqueue/work_usrthread.c,
    arch/avr/src/avrdx/avrdx_timerisr_tickless_alarm.c).
  - Strip CONFIG_SYSTEM_TIME64=y from every board defconfig.
  - Update Documentation/guides/rust.rst accordingly.

Signed-off-by: Xiang Xiao <xiaoxiang@xiaomi.com>

include/inttypes.h

@@ -338,36 +338,6 @@
 #define SCNxOFF     SCNx32
 #endif
 
-/* time_t */
-
-#ifdef CONFIG_SYSTEM_TIME64
-#define PRIdTM      PRId64
-#define PRIiTM      PRIi64
-#define PRIoTM      PRIo64
-#define PRIuTM      PRIu64
-#define PRIxTM      PRIx64
-#define PRIXTM      PRIX64
-
-#define SCNdTM      SCNd64
-#define SCNiTM      SCNi64
-#define SCNoTM      SCNo64
-#define SCNuTM      SCNu64
-#define SCNxTM      SCNx64
-#else
-#define PRIdTM      PRId32
-#define PRIiTM      PRIi32
-#define PRIoTM      PRIo32
-#define PRIuTM      PRIu32
-#define PRIxTM      PRIx32
-#define PRIXTM      PRIX32
-
-#define SCNdTM      SCNd32
-#define SCNiTM      SCNi32
-#define SCNoTM      SCNo32
-#define SCNuTM      SCNu32
-#define SCNxTM      SCNx32
-#endif
-
 /****************************************************************************
  * Type Definitions
  ****************************************************************************/

include/limits.h

@@ -236,11 +236,7 @@
 #define TIMER_MAX      _POSIX_TIMER_MAX
 #define CLOCKRES_MIN   _POSIX_CLOCKRES_MIN
 
-#ifdef CONFIG_SYSTEM_TIME64
-#  define CLOCK_MAX    UINT64_MAX
-#else
-#  define CLOCK_MAX    UINT32_MAX
-#endif
+#define CLOCK_MAX      UINT64_MAX
 
 /* Other invariant values */
 

include/nuttx/clock.h

@@ -225,8 +225,7 @@
 
 #define NSEC2MSEC(nsec)       div_const(nsec, (uint32_t)NSEC_PER_MSEC)
 
-#if defined(CONFIG_DEBUG_SCHED) && defined(CONFIG_SYSTEM_TIME64) && \
-    !defined(CONFIG_SCHED_TICKLESS)
+#if defined(CONFIG_DEBUG_SCHED) && !defined(CONFIG_SCHED_TICKLESS)
 /* Initial system timer ticks value close to maximum 32-bit value, to test
  * 64-bit system-timer after going over 32-bit value. This is to make errors
  * of casting 64-bit system-timer to 32-bit variables more visible.
@@ -307,11 +306,7 @@ struct cpuload_s
  * should be used only within the OS proper and not by portable applications.
  */
 
-#ifdef CONFIG_SYSTEM_TIME64
 typedef int64_t sclock_t;
-#else
-typedef int32_t sclock_t;
-#endif
 
 /****************************************************************************
  * Public Data

include/nuttx/fs/hostfs.h

@@ -136,11 +136,7 @@ typedef int          nuttx_fsid_t[2];
 
 /* These must match the definition in include/time.h */
 
-#  ifdef CONFIG_SYSTEM_TIME64
 typedef uint64_t     nuttx_time_t;
-#  else
-typedef uint32_t     nuttx_time_t;
-#  endif
 
 struct nuttx_timespec
 {

include/sys/types.h

@@ -251,13 +251,8 @@ typedef uint16_t     sa_family_t;
  * unsigned type is used to support the full range of the internal clock.
  */
 
-#ifdef CONFIG_SYSTEM_TIME64
 typedef uint64_t     clock_t;
 typedef uint64_t     time_t;         /* Holds time in seconds */
-#else
-typedef uint32_t     clock_t;
-typedef uint32_t     time_t;         /* Holds time in seconds */
-#endif
 typedef int          clockid_t;      /* Identifies one time base source */
 typedef FAR void    *timer_t;        /* Represents one POSIX timer */