FindMy: Refactors and improvements

- state handled reparately, decoupled from app
- better apple/samsung/unknown parsing and handling
- improve error handling
- add url to manifest + up stack size just in case

applications/system/findmy/findmy_state.h

@@ -0,0 +1,17 @@
+#pragma once
+
+#include <extra_beacon.h>
+
+typedef struct {
+    uint8_t mac[EXTRA_BEACON_MAC_ADDR_SIZE];
+    uint8_t data[EXTRA_BEACON_MAX_DATA_SIZE];
+    GapExtraBeaconConfig config;
+
+    bool beacon_active;
+    uint8_t broadcast_interval;
+    uint8_t transmit_power;
+} FindMyState;
+
+bool findmy_state_load(FindMyState* out_state);
+
+void findmy_state_apply(FindMyState* state);