Make MuonStandaloneRec work with hits and clusters

Template MuonStandaloneRec work with MuonCommonHit and MuonCluster, to be use for tag-and-probe tracking efficiency measurements. Also:

• Improve MuonStandaloneTrack
• Add the possibility of constraining y at z=0 in the fit of the track in the muon system.
• Introduce a converter from MuonHitContainer to std::vector<MuonCommonHit> to make MuonStandaloneRec compatible with hits and clusters.
• Add lower-case accessors in MuonCluster, to make it compatible with MuonCommonHit

Muon/MuonTools/src/MuonHitContainerToCommonMuonHits.cpp

@@ -16,6 +16,7 @@
 #include "Event/PrHits.h"
 #include "MuonDAQ/CommonMuonHit.h"
 #include "MuonDAQ/MuonHitContainer.h"
+#include <Detector/Muon/MuonConstants.h>
 
 namespace LHCb {
 
@@ -38,7 +39,7 @@ namespace LHCb {
     CommonMuonHits operator()( const MuonHitContainer& hitContainer ) const override {
       CommonMuonHits out;
       out.reserve( hitContainer.hits( 0 ).size() * LHCb::Detector::Muon::nStations );
-      for ( int s = 0; s < LHCb::Detector::Muon::nStations; ++s ) {
+      for ( std::size_t s = 0; s < LHCb::Detector::Muon::nStations; ++s ) {
         auto const& hits = hitContainer.hits( s );
         out.insert( out.end(), hits.begin(), hits.end() );
       }