Add telemetry_server plugin (#1482)

* Add telemetry_server plugin

* Remove GPS origin from telem server

* Add flight_mode support to telem_server

* Fix stabilize typo

* Move actions out of telem_server

* Fix casts, formatting & boot time units

* Fix style

* Update proto - remove RcReceiver

* Add return keyword to publish_status_text

* ...fix style

* Fix casting warnings (you will like static_casts)

Co-authored-by: Seb Horsewell <seb.horsewell@seebyte.com>

src/core/mavsdk_impl.h

@@ -83,6 +83,11 @@ class MavsdkImpl {
 
     double timeout_s() const { return _timeout_s; };
 
+    void set_base_mode(uint8_t base_mode);
+    void set_custom_mode(uint32_t custom_mode);
+    uint8_t get_base_mode() const;
+    uint32_t get_custom_mode() const;
+
     MAVLinkAddress own_address{};
 
 private:
@@ -143,6 +148,9 @@ class MavsdkImpl {
     void* _heartbeat_send_cookie{nullptr};
 
     std::atomic<bool> _should_exit = {false};
+
+    std::atomic<uint8_t> _base_mode = 0;
+    std::atomic<uint32_t> _custom_mode = 0;
 };
 
 } // namespace mavsdk