[FL-872] Furi, API-HAL, App-Loader cleanup and improvements (#334)

* Furi: replace obsolete furiac_exit with osThreadExit, drop obsolete apis and test. Rename systemd to flipper and move to separate file, cleanup. ApiHal: Rename timebase to os and move freertos hooks there, move insomnia api to power module.
* Furi: new thread helper
* Furi: cleanup thread documentation
* Flipper, AppLoader: update to use FuriThread. Update tasks signatures to match FuriThreadCallback signature.
* F4: rename API_HAL_TIMEBASE_DEBUG to API_HAL_OS_DEBUG
* Applications: rename FuriApplication to FlipperApplication, use FuriThreadCallback signature for apps.
* C++ app template sample, new exit method

applications/examples/vibro.c

@@ -21,7 +21,7 @@ static void button_handler(const void* value, void* _ctx) {
     }
 }
 
-void application_vibro(void* p) {
+int32_t application_vibro(void* p) {
     Ctx ctx = {.led = (GpioPin*)&led_gpio[1], .vibro = (GpioPin*)&vibro_gpio};
 
     gpio_init(ctx.led, GpioModeOutputOpenDrain);
@@ -37,4 +37,6 @@ void application_vibro(void* p) {
     while(1) {
         osDelay(osWaitForever);
     }
+
+    return 0;
 }