modules: cmsis: move glue code to modules/cmsis

The CMSIS module glue code was part of arch/ directory. Move it to
modules/cmsis, and provide a single entry point for it: cmsis_core.h.
This entry header will include the right CMSIS header (M or A/R).

To make this change possible, CMSIS module Kconfig/CMake are declared as
external, allowing us to add a new Zephyr include directory.

All files including CMSIS have been updated.

Signed-off-by: Gerard Marull-Paretas <gerard.marull@nordicsemi.no>

tests/application_development/code_relocation/src/main.c

@@ -17,7 +17,7 @@
  */
 
 #if (defined(CONFIG_ARM_MPU) && !defined(CONFIG_CPU_HAS_NXP_MPU))
-#include <zephyr/arch/arm/aarch32/cortex_m/cmsis.h>
+#include <cmsis_core.h>
 void disable_mpu_rasr_xn(void)
 {
 	uint32_t index;