Define fabric refmap json file

This prevents conflicts with other plugins that use mixins and define default refmap file.

Affects issues:
- Fixed #3106

Plan/fabric/build.gradle

@@ -30,6 +30,11 @@ dependencies {
     testImplementation project(path: ":common", configuration: 'testArtifacts')
 }
 
+loom {
+    // Defining separate refmap file prevents conflicts with plugin mixins
+    mixin.defaultRefmapName.set("plan-fabric-refmap.json")
+}
+
 tasks.withType(JavaCompile).configureEach {
     options.release.set(17)
 }

Plan/fabric/src/main/resources/plan.mixins.json

@@ -3,6 +3,7 @@
   "minVersion": "0.8",
   "package": "net.playeranalytics.plan.gathering.listeners.events.mixin",
   "compatibilityLevel": "JAVA_17",
+  "refmap": "plan-fabric-refmap.json",
   "mixins": [
     "ClientToServerHandshakePacketMixin",
     "KickCommandMixin",