Common/DebugInterface: Default virtual destructor

While we're at it, we can also default the constructor and destructor of
inheriting classes in their respective cpp file to prevent the
construction and destruction of non-trivial types being inlined into
other regions of code.

Source/Core/Core/Debugger/PPCDebugInterface.cpp

@@ -44,6 +44,9 @@ void PPCPatches::Patch(std::size_t index)
   }
 }
 
+PPCDebugInterface::PPCDebugInterface() = default;
+PPCDebugInterface::~PPCDebugInterface() = default;
+
 std::size_t PPCDebugInterface::SetWatch(u32 address, std::string name)
 {
   return m_watches.SetWatch(address, std::move(name));