ekf2: ev vel, use measurement timestamp to update aid_src timestamp_sample (#25774)

- the estimator_aid_src::sample_timestamp would use its own timestamp to update, this
  would cause the estimator_aid_src for ev velocity not to log, since the
timestamp_sample would always equal to zero and thus never be greater
than the previous published time

Co-authored-by: henrykotze <henry@autonosky.com>

src/modules/ekf2/EKF/aid_sources/external_vision/ev_vel.h

@@ -57,7 +57,7 @@ public:
 	virtual ~ExternalVisionVel() = default;
 	virtual bool fuseVelocity(estimator_aid_source3d_s &aid_src, float gate)
 	{
-		_ekf.fuseLocalFrameVelocity(aid_src, aid_src.timestamp, _measurement,
+		_ekf.fuseLocalFrameVelocity(aid_src, _sample.time_us, _measurement,
 					    _measurement_var, gate);
 		return aid_src.fused;