kernel: add k_thread_access_grant()

This is a runtime counterpart to K_THREAD_ACCESS_GRANT().
This function takes a thread and a NULL-terminated list of kernel
objects and runs k_object_access_grant() on each of them.
This function doesn't require any special permissions and doesn't
need to become a system call.

__attribute__((sentinel)) added to warn users if they omit the
required NULL termination.

Signed-off-by: Andrew Boie <andrew.p.boie@intel.com>