Move strip-kotlin-annotations script to buildSrc

... and invoke it directly in kotlin-reflect's build file, instead of
running another instance of compiler to evaluate a script. Also only
strip kotlin.Metadata, since it's the only annotation with heavy
metadata on Kotlin-generated class files

gradle/project-schema.json

@@ -4,9 +4,7 @@
             
         },
         "configurations": [
-            "bootstrapCompile",
-            "scriptCompile",
-            "scriptRuntime"
+            "bootstrapCompile"
         ],
         "extensions": {
             "ext": "org.gradle.api.plugins.ExtraPropertiesExtension",