Move legacy support classes to another jar

Signed-off-by: TheKodeToad <TheKodeToad@proton.me>

libraries/launcher/org/prismlauncher/legacy/LegacyProxy.java

@@ -0,0 +1,17 @@
+package org.prismlauncher.legacy;
+
+import org.prismlauncher.launcher.Launcher;
+import org.prismlauncher.utils.Parameters;
+
+// used as a fallback if NewLaunchLegacy is not on the classpath
+// if it is, this class will be replaced
+public final class LegacyProxy {
+
+    public static Launcher createLauncher(Parameters params) {
+        throw new AssertionError("NewLaunchLegacy is not loaded");
+    }
+
+    public static void applyOnlineFixes(Parameters params) {
+    }
+
+}