The K_HEAP_DEFINE macro would allow users to specify heaps that are
too small, leading to potential corruption events (though at least
there were __ASSERTs that would catch this at runtime if enabled).
It would be nice to put the logic to compute this value into the heap
code, but that isn't available in kernel.h (and we don't want to pull
it in as this header is already WAY to thick). So instead we just
hand-compute and document the choice. We can address bitrot problems
with a test.
(Tweaks to heap size asserts and correct size bounds from Nicolas Pitre)
Fixes#33009
Signed-off-by: Andy Ross <andrew.j.ross@intel.com>