feat(lp_core): add a public function to get the timer cycle count

Closes https://github.com/espressif/esp-idf/issues/13101

components/ulp/lp_core/shared/include/ulp_lp_core_lp_timer_shared.h

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2023 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2023-2024 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Apache-2.0
  */
@@ -11,6 +11,13 @@
 extern "C" {
 #endif
 
+/**
+ * @brief Get the number of cycle count for the LP timer
+ *
+ * @return current timer cycle count
+ */
+uint64_t ulp_lp_core_lp_timer_get_cycle_count(void);
+
 /**
  * @brief Sets the next wakeup alarm
  *