Minimize references to java.util.Collections in stdlib sources

Only three usages are left in platform-independent code: in reverse, sort and
sortWith for mutable lists

libraries/tools/kotlin-stdlib-gen/src/generators/GenerateStandardLib.kt

@@ -38,7 +38,6 @@ fun List<GenericFunction>.writeTo(file: File, builder: GenericFunction.() -> Str
         its.append("package kotlin.collections\n\n")
         its.append("$COMMON_AUTOGENERATED_WARNING\n\n")
         its.append("import java.util.*\n\n")
-        its.append("import java.util.Collections // TODO: it's temporary while we have java.util.Collections in js\n\n")
         for (t in this.sortedBy { it.signature }) {
             its.append(t.builder())
         }
@@ -59,7 +58,6 @@ fun List<ConcreteFunction>.writeTo(outDir: File, sourceFile: SourceFile) {
         its.append("$COMMON_AUTOGENERATED_WARNING\n\n")
         its.append("import kotlin.comparisons.*\n")
         its.append("import java.util.*\n\n")
-        its.append("import java.util.Collections // TODO: it's temporary while we have java.util.Collections in js\n\n")
 
         for (f in this) {
             f.textBuilder(its)

libraries/tools/kotlin-stdlib-gen/src/templates/Ordering.kt

@@ -33,7 +33,7 @@ fun ordering(): List<GenericFunction> {
             """
             if (this is Collection && size <= 1) return toList()
             val list = toMutableList()
-            Collections.reverse(list)
+            list.reverse()
             return list
             """
         }
@@ -42,7 +42,7 @@ fun ordering(): List<GenericFunction> {
             """
             if (isEmpty()) return emptyList()
             val list = toMutableList()
-            Collections.reverse(list)
+            list.reverse()
             return list
             """
         }