kernel: introduce supervisor-only stacks

These stacks are appropriate for threads that run purely in
supervisor mode, and also as stacks for interrupt and exception
handling.

Two new arch defines are introduced:

- ARCH_KERNEL_STACK_GUARD_SIZE
- ARCH_KERNEL_STACK_OBJ_ALIGN

New public declaration macros:

- K_KERNEL_STACK_RESERVED
- K_KERNEL_STACK_EXTERN
- K_KERNEL_STACK_DEFINE
- K_KERNEL_STACK_ARRAY_DEFINE
- K_KERNEL_STACK_MEMBER
- K_KERNEL_STACK_SIZEOF

If user mode is not enabled, K_KERNEL_STACK_* and K_THREAD_STACK_*
are equivalent.

Separately generated privilege elevation stacks are now declared
like kernel stacks, removing the need for K_PRIVILEGE_STACK_ALIGN.

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

arch/x86/core/intel64/thread.c

@@ -24,13 +24,7 @@ void arch_new_thread(struct k_thread *thread, k_thread_stack_t *stack,
 	struct x86_initial_frame *iframe;
 
 #if CONFIG_X86_STACK_PROTECTION
-	struct z_x86_thread_stack_header *header =
-		(struct z_x86_thread_stack_header *)stack;
-
-	/* Set guard area to read-only to catch stack overflows */
-	z_x86_mmu_set_flags(&z_x86_kernel_ptables, &header->guard_page,
-			    MMU_PAGE_SIZE, MMU_ENTRY_READ, Z_X86_MMU_RW,
-			    true);
+	z_x86_set_stack_guard(stack);
 #endif
 #ifdef CONFIG_USERSPACE
 	switch_entry = z_x86_userspace_prepare_thread(thread);