fix(unity): fixed name conflict in unity builds

getSpecies was defined in two translation units. This was not an issue
for regular builds but broke unity builds. this has been refactored to a
single function in utils.h

src/composition/lib/composition.cpp

@@ -34,6 +34,7 @@
 #include "fourdst/atomic/atomicSpecies.h"
 #include "fourdst/atomic/species.h"
 #include "fourdst/composition/composition.h"
+#include "fourdst/composition/utils.h"
 
 #include "fourdst/composition/exceptions/exceptions_composition.h"
 
@@ -62,13 +63,6 @@ namespace {
         return sorted;
     }
 
-    std::optional<fourdst::atomic::Species> getSpecies(const std::string& symbol) {
-        if (!fourdst::atomic::species.contains(symbol)) {
-            return std::nullopt;
-        }
-        return fourdst::atomic::species.at(symbol);
-    }
-
     void throw_unknown_symbol(quill::Logger* logger, const std::string& symbol) {
         LOG_ERROR(logger, "Symbol {} is not a valid species symbol (not in the species database)", symbol);
         throw fourdst::composition::exceptions::UnknownSymbolError("Symbol " + symbol + " is not a valid species symbol (not in the species database)");