test_vtol_mission: Add additional testing for VTOL RTL and reverse mission RTL

mavsdk-test: added a vtol mission without a landing at the end (used for reversed RTL)
math_helpers: added function to compute local position from a raw mission item

Signed-off-by: RomanBapst <bapstroman@gmail.com>

test/mavsdk_tests/CMakeLists.txt

@@ -17,6 +17,7 @@ if(MAVSDK_FOUND)
         test_main.cpp
         autopilot_tester.cpp
         autopilot_tester_failure.cpp
+        autopilot_tester_rtl.cpp
         # follow-me needs a MAVSDK update:
         # https://github.com/mavlink/MAVSDK/pull/1770
         # autopilot_tester_follow_me.cpp