doc: reference: terminology: refine API attributes
doc: reference: terminology: refine API attributes

The original description for isr-ok allowed the function to return an
error if called from an interrupt context, rather than doing its job.
This led to complex descriptions like "isr-ok but not sleep" to
indicate that the function could be called from thread or interrupt
context without visible behavior changes, including returning an
error based on calling context.

Remove the special terminology for cases where a function returns an
error (rather than causing undefined behavior) when invoked from an
interrupt or pre-kernel.  Redefine isr-ok to indicate that the call
does what it's supposed to do regardless of interrupt or thread
context, delegating the description of allowed behaviors to the API
documentation (which should explicitly note when it's allowed to fail
to perform in non-thread context).

This also makes more clear that isr-ok applies to functions regardless
of whether they can cause an invoking thread to context switch.

Signed-off-by: Peter Bigot <a4112a160b558d5427af084318038e19a95979ee@nordicsemi.no>

nashif/zephyr,Vudentz/zephyr,nashif/zephyr,galak/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,finikorg/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,nashif/zephyr,nashif/zephyr,Vudentz/zephyr,galak/zephyr,finikorg/zephyr,Vudentz/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,finikorg/zephyr,Vudentz/zephyr,galak/zephyr