rtos: rework rtos_create()

rtos: rework rtos_create()

To simplify the caller of rtos_create(), convert the code from
jimtcl oriented to OpenOCD commands.

While there, fix inconsistencies in almost every rtos create()
method and reset rtos_auto_detect to better cooperate on run-time
rtos configuration.

Change-Id: I59c443aaed77a48174facdfc86db75d6b28c8480
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-on: https://review.openocd.org/c/openocd/+/8830
Tested-by: jenkins