Add ADL-based field traits, migrate all call sites, remove cafInternalPdmValueFieldSpecializations.h

Introduce cafPdmFieldTraits.h with ADL-based pdmToVariant/pdmFromVariant/pdmVariantEqual
as a replacement for PdmValueFieldSpecialization. Migrate all types (AppEnum, FilePath,
PdmPointer, cvf types) and all call sites (PdmDataValueField, PdmProxyValueField, UI
framework, ApplicationLibCode). Delete cafInternalPdmValueFieldSpecializations.h.
Add cafPdmFieldTraits unit tests and fix std::optional support.

ApplicationLibCode/ProjectDataModel/RimDataSourceSteppingTools.h

@@ -20,6 +20,7 @@
 
 #include "RifEclipseSummaryAddressDefines.h"
 
+#include "cafPdmOptionItemInfo.h"
 #include "cafPdmUiItem.h"
 #include "cafPdmValueField.h"
 

ApplicationLibCode/ProjectDataModel/WellPath/RimWellPathGeometryDef.cpp

@@ -520,7 +520,7 @@ void RimWellPathGeometryDef::fieldChangedByUi( const caf::PdmFieldHandle* change
                               linkedDefs.end() );
 
             cvf::Vec3d oldPos;
-            caf::PdmValueFieldSpecialization<cvf::Vec3d>::setFromVariant( oldValue, oldPos );
+            caf::pdmFromVariant( oldValue, oldPos );
 
             auto delta = m_referencePointUtmXyd() - oldPos;