!nuttx: drop redundant casts on tv_sec/tv_nsec and fix printf formats

Now that time_t is unconditionally 64-bit (signed int64_t) and the
struct timespec fields tv_sec / tv_nsec are wide enough on their own,
the explicit (uint64_t)/(int64_t)/(int) casts that used to guard the
multiplications and subtractions in *_us / *_ms / *_ns helpers are no
longer needed.  Drop them to keep the timekeeping math readable and
consistent with the previous sclock_t/time_t cleanup.

In the same spirit, this commit also:

* Normalises the printf-style format specifiers and casts used to
  print tv_sec / tv_nsec / tv_usec values across arch/, drivers/,
  fs/, sched/ and libs/.  The prior code was a mix of
  "%d"/"%u"/"%ld"/"%lu"/"%lld"/PRIu32/PRIu64 with matching
  (int)/(unsigned long)/(long long)/PRIu* casts; some formats
  truncated time_t on 32-bit hosts, others mismatched signedness or
  width.  Replace all such cases with the portable POSIX-recommended
  forms:

    - tv_sec  (time_t,       signed, impl-defined width) -> %jd  + (intmax_t)
    - tv_nsec (long,         signed)                     -> %ld  (no cast)
    - tv_usec (suseconds_t / long)                       -> %ld  (no cast)

  Add #include <stdint.h> where required.

* Drops a few stale `(FAR const time_t *)&ts.tv_sec` casts and
  related `(FAR struct tm *)` / `(const time_t *)` casts in
  gmtime_r() / localtime_r() / gmtime() callers; ts.tv_sec is plain
  time_t now and the casts only obscured the type.

* Fixes one overflow in fs/procfs/fs_procfscritmon.c where
  all_time.tv_sec * 1000000 could overflow on 32-bit time_t before
  being multiplied again; cast to uint64_t at the start.

No behavioural change.

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

libs/libc/time/lib_gethrtime.c

@@ -49,5 +49,5 @@ hrtime_t gethrtime(void)
   struct timespec ts;
 
   clock_gettime(CLOCK_MONOTONIC, &ts);
-  return (hrtime_t)1000000000 * ts.tv_sec + ts.tv_nsec;
+  return 1000000000 * ts.tv_sec + ts.tv_nsec;
 }