[FL-2480] Use SysTick as the main OS timer (#1140)

* Use SysTick as OS tick timer
* Use LPTIM2 as tickless idle timer
* Remove dummy LPTIM2 IRQ handler
* Clean up clock init code
* Rename os timer to idle timer
* Advance hal ticks along with FreeRTOS's
* Improve SysTick control during tickless idle
* Improve idle timer precision
* Correct SysTick IRQ priority
* Main, FuriHal: move system startup to separate thread
* Minor code cleanup

Co-authored-by: Aleksandr Kutuzov <alleteam@gmail.com>

firmware/targets/f7/furi_hal/furi_hal_os.h

@@ -11,6 +11,10 @@ extern "C" {
  */
 void furi_hal_os_init();
 
+/* Advance OS tick counter
+ */
+void furi_hal_os_tick();
+
 #ifdef __cplusplus
 }
-#endif
+#endif