file-sys: Default heavy-weight class destructors in the cpp file

Several classes have a lot of non-trivial members within them, or don't
but likely should have the destructor defaulted in the cpp file for
future-proofing/being more friendly to forward declarations.

Leaving the destructor unspecified allows the compiler to inline the
destruction code all over the place, which is generally undesirable from
a code bloat perspective.

src/core/file_sys/patch_manager.h

@@ -34,6 +34,7 @@ std::string FormatPatchTypeName(PatchType type);
 class PatchManager {
 public:
     explicit PatchManager(u64 title_id);
+    ~PatchManager();
 
     // Currently tracked ExeFS patches:
     // - Game Updates