GH-1795 add terminal launch option to use a specific Minecraft profile

Used like this:
```
./MultiMC --launch 1.17.1 --profile MultiMCTest --server mc.hypixel.net
```

launcher/LauncherMessage.h

@@ -0,0 +1,13 @@
+#pragma once
+
+#include <QString>
+#include <QMap>
+#include <QByteArray>
+
+struct LauncherMessage {
+    QString command;
+    QMap<QString, QString> args;
+
+    QByteArray serialize();
+    void parse(const QByteArray & input);
+};