Add R4 version of MDT hough transform

Add a first version of the Muon Hough transform for the WIP Phase-2 muon reconstruction. Use ACTS as back-end, while detector-specific work is handled in athena.

Also add validation package and required event data classes.

Documentation has been presented in the ITK Acts integration meeting.

Large MR since required ACTS version in Externals only recently arrived. Further development will happen in smaller MR.

MuonSpectrometer/MuonPhaseII/MuonPatternRecognition/MuonPatternRecognitionAlgs/src/MuonHoughTransformAlg.cxx

@@ -68,13 +68,11 @@ StatusCode MuonHoughTransformAlg::execute(const EventContext& ctx) const {
       ATH_CHECK(prepareHoughPlane(data)); 
       /// now perform the actual HT for each station
       for (auto&[stationId, stationHough] : data.houghSpaces){
-          ATH_CHECK(processStationHough(data, stationHough)); 
+          ATH_CHECK(processStationHough(data, stationHough));
+          /// write the maxima we found 
+          writeMaxima->emplace(StationHoughMaxima(stationId, stationHough.maxima)); 
       }
-
-    // write the maxima we found 
-    for (auto & [station, foundMax] : data.maxima){
-      writeMaxima->emplace(StationHoughMaxima(station,foundMax));
-    }
+     
     return StatusCode::SUCCESS;
 
 }
@@ -174,23 +172,19 @@ StatusCode MuonHoughTransformAlg::execute(const EventContext& ctx) const {
     }
     
 
-    auto max = data.peakFinder->findPeaks(*(data.houghPlane), data.currAxisRanges);
-    if (max.size() > 0) writeMaxima(station, data, max); 
-
-    return StatusCode::SUCCESS;
-  } 
-
-void MuonHoughTransformAlg::writeMaxima(const StationIdentifier & station, MuonHoughEventData & data, const std::vector<ActsPeakFinderForMuon::Maximum> & maxima) const{
-    auto [ iter, added] = data.maxima.emplace(station, std::vector<MuonR4::HoughMaximum>{});
-    iter->second.reserve(maxima.size());  
-    for (const auto & max : maxima){
+    auto maxima = data.peakFinder->findPeaks(*(data.houghPlane), data.currAxisRanges);
+    if (maxima.empty()) {
+      return StatusCode::SUCCESS;
+    }
+    for (const auto & max : maxima) {
       /// TODO: Proper weighted hit counting... 
       std::vector<const xAOD::UncalibratedMeasurement*> hitList; 
       hitList.insert(hitList.end(), max.hitIdentifiers.begin(), max.hitIdentifiers.end()); 
-      iter->second.emplace_back(max.x, max.y, hitList.size(), std::move(hitList));
+      currentStation.maxima.emplace_back(max.x, max.y, hitList.size(), std::move(hitList));
     } 
-}
-
+   
+    return StatusCode::SUCCESS;
+  } 
 
 void MuonHoughTransformAlg::fillFromDriftCircle(MuonHoughEventData & data, const xAOD::MdtDriftCircle* driftCircle) const{  
       data.houghPlane->fill<xAOD::MdtDriftCircle>(*driftCircle,