MissionFeasibility: add combined takeoff/landing requirement check

Replace the existing check for the availability of a takeoff mission item with a combined
check for takeoff and landing item (or landing pattern). New param MIS_TKO_LAND_REQ
can be set to require only a takeoff, only a landing, both takeoff and landing, and
both or none. The latter is meant to be set if is e.g. deemed unsafe to start a flight
through a Takeoff WP without though defining a Landing - as then in case of a RTL the
vehicle doesn't follow a pre-defined path but instead only can do default RTL that especially
for FW and VTOL isn't always safe.

Signed-off-by: Silvan Fuhrer <silvan@auterion.com>

src/modules/navigator/mission_params.c

@@ -58,14 +58,19 @@
 PARAM_DEFINE_FLOAT(MIS_TAKEOFF_ALT, 2.5f);
 
 /**
- * Take-off waypoint required
+ * Mission takeoff/landing required
  *
- * If set, the mission feasibility checker will check for a takeoff waypoint on the mission.
+ * Specifies if a mission has to contain a takeoff and/or mission landing.
+ * Validity of configured takeoffs/landings is checked independently of the setting here.
  *
- * @boolean
+ * @value 0 No requirements
+ * @value 1 Require a takeoff
+ * @value 2 Require a landing
+ * @value 3 Require a takeoff and a landing
+ * @value 4 Require a takeoff and a landing, or neither of both
  * @group Mission
  */
-PARAM_DEFINE_INT32(MIS_TAKEOFF_REQ, 0);
+PARAM_DEFINE_INT32(MIS_TKO_LAND_REQ, 0);
 
 /**
  * Minimum Loiter altitude