[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_delay.c

@@ -6,8 +6,6 @@
 
 #define TAG "FuriHalDelay"
 
-static volatile uint32_t tick_cnt = 0;
-
 void furi_hal_delay_init() {
     CoreDebug->DEMCR |= CoreDebug_DEMCR_TRCENA_Msk;
     DWT->CTRL |= DWT_CTRL_CYCCNTENA_Msk;
@@ -18,12 +16,8 @@ uint32_t furi_hal_delay_instructions_per_microsecond() {
     return SystemCoreClock / 1000000;
 }
 
-void furi_hal_tick(void) {
-    tick_cnt++;
-}
-
 uint32_t furi_hal_get_tick(void) {
-    return tick_cnt;
+    return osKernelGetTickCount();
 }
 
 uint32_t furi_hal_ms_to_ticks(float milliseconds) {