Move UArraysKt into kotlin.collections.unsigned package

Provide UArraysKt class in kotlin.collections for binary compatibility
instead of removed multipart facade class. It contains only non-inline
functions of the latter.

libraries/tools/kotlin-stdlib-gen/src/templates/dsl/SourceFile.kt

@@ -5,10 +5,10 @@
 
 package templates
 
-enum class SourceFile(jvmClassName: String? = null, val multifile: Boolean = true, val packageName: String? = null) {
+enum class SourceFile(jvmClassName: String? = null, val multifile: Boolean = true, val packageName: String? = null, val jvmPackageName: String? = null) {
 
     Arrays(packageName = "kotlin.collections"),
-    UArrays(packageName = "kotlin.collections"),
+    UArrays(packageName = "kotlin.collections", jvmPackageName = "kotlin.collections.unsigned"),
     Collections(packageName = "kotlin.collections"),
     UCollections(packageName = "kotlin.collections"),
     Sets(packageName = "kotlin.collections"),

libraries/tools/kotlin-stdlib-gen/src/templates/dsl/Writers.kt

@@ -84,6 +84,9 @@ fun List<MemberBuilder>.writeTo(file: File, targetedSource: TargetedSourceFile)
                 }
 
                 writer.appendln("@file:kotlin.jvm.JvmName(\"${sourceFile.jvmClassName}\")")
+                sourceFile.jvmPackageName?.let {
+                    writer.appendln("@file:kotlin.jvm.JvmPackageName(\"$it\")")
+                }
                 writer.appendln()
             }
         }