Change load method to Loader's entrypoints (#497)

* Start moving away from noop mixins

Remove the mixin from the json list

* Change startup method to Loader entrypoints

src/main/resources/carpet.mixins.json

@@ -4,7 +4,6 @@
   "package": "carpet.mixins",
   "compatibilityLevel": "JAVA_8",
   "mixins": [
-    "CrashReport_coreMixin",
     "SpawnHelperInnerMixin",
     "CommandManagerMixin",