[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/Src/main.c

@@ -6,32 +6,31 @@
 
 #define TAG "Main"
 
-#ifdef FURI_RAM_EXEC
-int main() {
-    // Initialize FURI layer
-    furi_init();
-
-    // Flipper critical FURI HAL
-    furi_hal_init_early();
+static const osThreadAttr_t init_thread_attr = {
+    .name = "Init",
+    .stack_size = 4096,
+};
 
+void init_task() {
     // Flipper FURI HAL
     furi_hal_init();
 
     // Init flipper
     flipper_init();
 
-    furi_run();
-
-    while(1) {
-    }
+    osThreadExit();
 }
-#else
+
 int main() {
     // Initialize FURI layer
     furi_init();
 
     // Flipper critical FURI HAL
     furi_hal_init_early();
+
+#ifdef FURI_RAM_EXEC
+    osThreadNew(init_task, NULL, &init_thread_attr);
+#else
     furi_hal_light_sequence("RGB");
 
     // Delay is for button sampling
@@ -52,21 +51,16 @@ int main() {
         furi_hal_power_reset();
     } else {
         furi_hal_light_sequence("rgb G");
-
-        // Flipper FURI HAL
-        furi_hal_init();
-
-        // Init flipper
-        flipper_init();
-
-        furi_run();
+        osThreadNew(init_task, NULL, &init_thread_attr);
     }
-
-    while(1) {
-    }
-}
 #endif
 
+    // Run Kernel
+    furi_run();
+
+    furi_crash("Kernel is Dead");
+}
+
 void Error_Handler(void) {
     furi_crash("ErrorHandler");
 }