ENH: vector mag(), magSqr() methods - complementary to dist(), distSqr()

ENH: use direct access to pointHit as point(), use dist(), distSqr()

- if the pointHit has already been checked for hit(), can/should
  simply use point() noexcept access subsequently to avoid redundant
  checks. Using vector distSqr() methods provides a minor optimization
  (no itermediate temporary), but can also make for clearer code.

ENH: copy construct pointIndexHit with different index

- symmetric with constructing from a pointHit with an index

STYLE: prefer pointHit point() instead of rawPoint()

applications/utilities/preProcessing/viewFactorsGen/shootRays.H

@@ -146,7 +146,7 @@ for (const int proci : Pstream::allProcs())
                 if (aggHitIndex[hitIndex] == startAgg[rayID])
                 {
                     const vector& endP = end[rayID];
-                    const vector& startP = hitInfo[hitIndex].hitPoint();
+                    const vector& startP = hitInfo[hitIndex].point();
                     const vector& d = endP - startP;
 
                     startHitItself.append(startP + 0.01*d);