Move RequireKotlinNames to 'descriptors'

Also move version string regex there and rename the class to
RequireKotlinConstants. This allows to get rid of dependency of
'serialization' on 'frontend'.

core/descriptors/src/org/jetbrains/kotlin/resolve/RequireKotlinConstants.kt

@@ -0,0 +1,21 @@
+/*
+ * Copyright 2010-2020 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.resolve
+
+import org.jetbrains.kotlin.name.FqName
+import org.jetbrains.kotlin.name.Name
+
+object RequireKotlinConstants {
+    val FQ_NAME = FqName("kotlin.internal.RequireKotlin")
+
+    val VERSION = Name.identifier("version")
+    val MESSAGE = Name.identifier("message")
+    val LEVEL = Name.identifier("level")
+    val VERSION_KIND = Name.identifier("versionKind")
+    val ERROR_CODE = Name.identifier("errorCode")
+
+    val VERSION_REGEX: Regex = "(0|[1-9][0-9]*)".let { number -> Regex("$number\\.$number(\\.$number)?") }
+}