Runtime: Add more usages of explicit

Prevents error-prone implicit conversions where applicable.

This targets the regular RuntimeCommon target this time around.

Runtime/Audio/CAudioGroupSet.hpp

@@ -21,7 +21,7 @@ class CAudioGroupSet {
   amuse::AudioGroupData LoadData();
 
 public:
-  CAudioGroupSet(std::unique_ptr<u8[]>&& in);
+  explicit CAudioGroupSet(std::unique_ptr<u8[]>&& in);
   const amuse::AudioGroupData& GetAudioGroupData() const { return m_data; }
   std::string_view GetName() const { return x20_name; }
 };