Advertise fast for at least 30 secs then slow down

On power up, advertise aggressively for at least 30 seconds then switch
to a longer interval to conserve battery life. This fast/slow pattern
is designed to balance connection response time and battery life.

When a disconnect event is received restart the fast/slow pattern.

When a failed connect event is received, restart the fast/slow pattern.

When the screen is activated and ble is not connected, restart the fast/slow pattern.

This pattern is consistent with Apple's BLE developer standards (QA 1931).

src/components/ble/NimbleController.h

@@ -72,6 +72,10 @@ namespace Pinetime {
       uint16_t connHandle();
       void NotifyBatteryLevel(uint8_t level);
 
+      void RestartFastAdv() {
+        fastAdvCount = 0;
+      }
+
     private:
       static constexpr const char* deviceName = "InfiniTime";
       Pinetime::System::SystemTask& systemTask;
@@ -94,6 +98,7 @@ namespace Pinetime {
 
       uint8_t addrType; // 1 = Random, 0 = PUBLIC
       uint16_t connectionHandle = BLE_HS_CONN_HANDLE_NONE;
+      uint8_t fastAdvCount = 0;
 
       ble_uuid128_t dfuServiceUuid {
         .u {.type = BLE_UUID_TYPE_128},