SelectivePacker: Consistently check whether TES entries are explicitly requested

SelectivePacker only explicitly checked whether KeyedContainers and RecSummary it had access to were explicitly requested -- other TES entries were added to the packed output regardless of any request, as soon as they existed in the TES. This MR moves this check 'upstream' in the code so that this is done in the same place for every type of object.

As a result, it may be that objects other than KeyedContainer and RecSummary are no longer implicitly copied, and the configuration may need to be adapted to explicitly copy them instead. To help with this, a new property 'AlwaysPack' has been added which specifies locations that should be packed regardless of any Hlt/Spruce decisions.

Must be applied in conjunction with Moore!2281 (merged) -- which also depends on !4149 (merged)

Event/EventPacker/src/component/SelectivePacker.cpp

@@ -669,7 +669,10 @@ namespace LHCb {
 
         Packer& packer() { return m_packer; }
 
-        bool emplace( Entry const* v ) { return m_set.emplace( *v ).second; }
+        bool emplace( Entry const* v ) {
+          assert( v != nullptr );
+          return m_set.emplace( *v ).second;
+        }
 
         void append_to( Buffer& buffer, Encoder& encoder, bool check,
                         LHCb::Hlt::PackedData::PackedDataChecksum* checksum ) const {
@@ -917,7 +920,15 @@ namespace LHCb {
 
       template <typename Container>
       void add( VOC<Container*> const& c ) {
-        for ( const auto& i : c ) add( i );
+        for ( const auto* i : c ) {
+          if ( !i ) continue;
+          if ( auto reg = i->registry(); !reg || !is_explicitly_requested( identifier( *reg ) ) ) {
+            m_lists.template get<Container>().packer().parent().debug()
+                << " skipping " << ( reg ? identifier( *reg ) : "no registry" ) << endmsg;
+            continue;
+          }
+          add( *i );
+        }
       }
 
       template <typename V>
@@ -927,19 +938,10 @@ namespace LHCb {
 
       template <typename V, typename M>
       void add( const KeyedContainer<V, M>& kc ) {
-        auto r = kc.registry();
-        if ( r && is_explicitly_requested( identifier( *r ) ) ) {
-          for ( const auto& i : kc ) add( i );
-        } else {
-          // std::cerr << "skipped " << identifier( kc ) << std::endl; TODO: add  a counter for each input location, and
-          // count how often it is requested...
-        }
+        for ( const auto& i : kc ) add( i );
       }
 
-      void add( const RecSummary& rs ) {
-        auto r = rs.registry();
-        if ( r && is_explicitly_requested( identifier( *r ) ) ) m_lists.add( rs );
-      }
+      void add( const RecSummary& rs ) { m_lists.add( rs ); }
 
       void add( const MCParticle& /*p*/ ) {
         // foe now, assume MCParticles are somehow packed elsewhere...