IniFile: Make Section's string constructor instances take strings by value

As the name is immediately stored into a class member, a move here is a
better choice.

This also moves the constructor implementations into the cpp file to
avoid an otherwise unnecessary inclusion in the header. This is also
likely a better choice as Section contains several non-trivial members,
so this would avoid potentially inlining a bunch of setup and teardown
code related to them as a side-benefit.

Source/Core/Common/IniFile.cpp

@@ -39,6 +39,12 @@ void IniFile::ParseLine(const std::string& line, std::string* keyOut, std::strin
 
 const std::string& IniFile::NULL_STRING = "";
 
+IniFile::Section::Section() = default;
+
+IniFile::Section::Section(std::string name_) : name{std::move(name_)}
+{
+}
+
 void IniFile::Section::Set(const std::string& key, const std::string& newValue)
 {
   auto it = values.find(key);