feat: Add parameter getters to TrackProxy (#1869)

This allows accessing the raw parameter elements by named methods, and to derive properties like absolute and transverse momentum.

Anything else that comes to mind we should add at this point?

Core/include/Acts/EventData/Track.hpp

@@ -8,8 +8,13 @@
 
 #pragma once
 
+#include "Acts/Definitions/Algebra.hpp"
+#include "Acts/Definitions/TrackParametrization.hpp"
+#include "Acts/Definitions/Units.hpp"
+#include "Acts/EventData/Charge.hpp"
 #include "Acts/EventData/MultiTrajectory.hpp"
 #include "Acts/Utilities/HashedString.hpp"
+#include "Acts/Utilities/UnitVectors.hpp"
 
 #include <any>
 #include <cstddef>
@@ -206,6 +211,58 @@ class TrackProxy {
     return m_container->covariance(m_index);
   }
 
+  ActsScalar charge() const {
+    // Currently, neutral tracks are not supported here
+    // @TODO: Evaluate if/how neutral 'tracks' should be accounted for
+    return SinglyCharged{}.extractCharge(parameters()[eBoundQOverP]);
+  }
+
+  /// Access the theta parameter of the track at the reference surface
+  /// @return The theta parameter
+  ActsScalar theta() const { return parameters()[eBoundTheta]; }
+
+  /// Access the phi parameter of the track at the reference surface
+  /// @return The phi parameter
+  ActsScalar phi() const { return parameters()[eBoundPhi]; }
+
+  /// Access the loc0 parameter of the track at the reference surface
+  /// @return The loc0 parameter
+  ActsScalar loc0() const { return parameters()[eBoundLoc0]; }
+
+  /// Access the loc1 parameter of the track at the reference surface
+  /// @return The loc1 parameter
+  ActsScalar loc1() const { return parameters()[eBoundLoc1]; }
+
+  /// Access the time parameter of the track at the reference surface
+  /// @return The time parameter
+  ActsScalar time() const { return parameters()[eBoundTime]; }
+
+  /// Access the q/p (curvature) parameter of the track at the reference surface
+  /// @return The q/p parameter
+  ActsScalar qOverP() const { return parameters()[eBoundQOverP]; }
+
+  /// Get the absolute momentum of the tack
+  /// @return The absolute track momentum
+  ActsScalar absoluteMomentum() const {
+    return SinglyCharged{}.extractMomentum(qOverP());
+  }
+
+  /// Get the transverse momentum of the track
+  /// @return The track transverse momentum value
+  ActsScalar transverseMomentum() const {
+    return std::sin(theta()) * absoluteMomentum();
+  }
+
+  /// Get a unit vector along the track direction at the reference surface
+  /// @return The direction unit vector
+  Vector3 unitDirection() const {
+    return makeDirectionUnitFromPhiTheta(phi(), theta());
+  }
+
+  /// Get the global momentum vector
+  /// @return the global momentum vector
+  Vector3 momentum() const { return absoluteMomentum() * unitDirection(); }
+
   /// Get a range over the track states of this track. Return value is
   /// compatible with range based for loop. Const version
   /// @return Track state range to iterate over