kernel/sched: Add timing.h support to thread_usage
kernel/sched: Add timing.h support to thread_usage

The runtime stats feature has always supported this, so use the same
kconfig to indirect the timing source in the same way.

(Personally I'm not a fan of the "timing" API, which really doesn't do
anything that the existing core "cycles" API does not except add a
bunch of code due to the separate implementation of frequency
management and conversion routines.  It comes from an era where
"cycles" were fixed to a MHz frequency clock on platforms like x86 yet
we had benchmarks that wanted to use the TSC.  Those days are behind
us and "cycles" can be fast everywhere.)

Signed-off-by: Andy Ross <c70f9a6bf6ee0cd69c8af4ce5e6b131945769315@intel.com>

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