fw pos ctrl: rework manual takeoff aid

- takeoff situational knowledge removed from all other modes except manual (or actual takeoff mode)
- manual takeoff is marked complete if at a controllable airspeed
- minimum pitch bounds TECS until manual takeoff complete
- remove individual roll constraints during manual takeoff (ground proximity constraints coming in subsequent commit)

src/modules/fw_pos_control_l1/FixedwingPositionControl.hpp

@@ -145,6 +145,9 @@ static constexpr float MAX_WEIGHT_RATIO = 2.0f;
 // air density of standard athmosphere at 5000m above mean sea level [kg/m^3]
 static constexpr float AIR_DENSITY_STANDARD_ATMOS_5000_AMSL = 0.7363f;
 
+// [rad] minimum pitch while airspeed has not yet reached a controllable value in manual position controlled takeoff modes
+static constexpr float MIN_PITCH_DURING_MANUAL_TAKEOFF = 0.0f;
+
 class FixedwingPositionControl final : public ModuleBase<FixedwingPositionControl>, public ModuleParams,
 	public px4::WorkItem
 {
@@ -265,6 +268,9 @@ private:
 	// [us] time at which the plane went in the air
 	hrt_abstime _time_went_in_air{0};
 
+	// indicates whether we have completed a manual takeoff in a position control mode
+	bool _completed_manual_takeoff{false};
+
 	// Takeoff launch detection and runway
 	LaunchDetector _launchDetector;
 	LaunchDetectionResult _launch_detection_state{LAUNCHDETECTION_RES_NONE};
@@ -409,9 +415,11 @@ private:
 	float getManualHeightRateSetpoint();
 
 	/**
-	 * @brief Check if we are in a takeoff situation
+	 * @brief Updates a state indicating whether a manual takeoff has been completed.
+	 *
+	 * Criteria include passing an airspeed threshold and not being in a landed state. VTOL airframes always pass.
 	 */
-	bool in_takeoff_situation();
+	void updateManualTakeoffStatus();
 
 	/**
 	 * @brief Update desired altitude base on user pitch stick input