[Platform API] Clean-up some usages of Platform

Mostly unused imports. Also, in some places,
TargetPlatform/MultiTargetPlatform were just passed around without
actually using (e.g. in deserialization)

compiler/frontend.java/src/org/jetbrains/kotlin/resolve/jvm/JvmResolverForModuleFactory.kt

@@ -120,7 +120,4 @@ object JvmResolverForModuleFactory : ResolverForModuleFactory() {
 
         return ResolverForModule(CompositePackageFragmentProvider(providersForModule), container)
     }
-
-    override val targetPlatform: TargetPlatform
-        get() = JvmPlatform
 }