change(xtensa): Deprecate ".../xtensa_timer.h" include path

This commit deprecates the "freertos/xtensa_timer.h" and "xtensa/xtensa_timer.h"
include paths. Users should use "xtensa_timer.h" instead.

- Replace legacy include paths
- Removed some unnecessary includes of "xtensa_timer.h"
- Add warning to compatibility header

components/mbedtls/test_apps/main/test_aes_sha_rsa.c

@@ -14,7 +14,6 @@
 #include "freertos/FreeRTOS.h"
 #include "freertos/task.h"
 #include "freertos/semphr.h"
-#include "freertos/xtensa_timer.h"
 #include "unity.h"
 #include "test_utils.h"
 #include "esp32/rom/sha.h"