The top command was added to nshlib in 2024 but was never documented.
Add a section to the NSH commands page covering syntax, options,
example output and configuration dependencies, including the
Linux-like summary header.
Also enable the command in the linum-stm32h753bi:nsh config: procfs,
CPU load measurement, stack coloration and task names, so that top
and ps are fully functional out of the box. This requires a dedicated
interrupt stack and larger IDLE/init task stacks: with SCHED_CPULOAD
the per-tick accounting runs in interrupt context, and with
ARCH_INTERRUPTSTACK=0 it lands on the stack of the interrupted task,
overflowing the 1 KiB IDLE stack and corrupting the adjacent heap.
Also add the VT100 escape sequences used by the top command screen
refresh as string literals in include/nuttx/vt100.h (VT100_STR_*),
next to the existing VT100_FMT_* definitions.
Tested on hardware.
Signed-off-by: Jorge Guzman <jorge.gzm@gmail.com>