stonecutter: setup project for multiversion support

- Switch to Stonecutter build system
- Migrate mappings to Mojmap

buildSrc/build.gradle.kts

@@ -0,0 +1,8 @@
+plugins {
+    `kotlin-dsl`
+    kotlin("jvm") version "2.0.20"
+}
+
+repositories {
+    mavenCentral()
+}