rfc: New SeString classes about dalamud

[Soreepeong]

For event delegates:

ref struct LazySeString {
    public readonly ReadOnlySpan<byte> Data;
    
    private ref SeString? instance;

    public LazySeString(ref SeString? buf) => this.instance = ref buf;
    
    public SeString SeString { get => this.instance ??= SeString.From(this.Data); }
}

So that SeStrings do not get parsed unnecessarily when no callee needs it.

[Haselnussbomber]

Reminder to use MacroCode and LinkMacroPayloadType names for payload names. 🙂