RTC: Simplify the RTC driver interface.  Way too much stuff in that interface and it is not fully implemented anywhere.

CONFIG_DEV_RANDOM depends on CONFIG_ARCH_HAVE_RNG which is selected with MCU-specific RNG H/W is enabled.  So correct default is y; you almost certainly want /dev/random as well.

Add file missed in last commit; sched_lock() and sched_mergepending() now use sched_mergeprioritized()

Add library functions to concatenate and move lists.  Add scheduler function to merge prioritized function to merge prioritized lists (not yet used).

Fix issues detected by cppcheck