Refactor boolean IR ABI stability flag to enum

Introduce an enum DeserializedContainerAbiStability with two values.
This is needed in order to support another reason for ABI instability in
a subsequent commit, namely "unstable because compiled by FIR".

 #KT-43592

compiler/config.jvm/src/org/jetbrains/kotlin/config/JVMConfigurationKeys.java

@@ -117,8 +117,8 @@ public class JVMConfigurationKeys {
     public static final CompilerConfigurationKey<List<String>> KLIB_PATHS =
             CompilerConfigurationKey.create("Paths to .klib libraries");
 
-    public static final CompilerConfigurationKey<Boolean> IS_IR_WITH_STABLE_ABI =
-            CompilerConfigurationKey.create("Is IR with stable ABI");
+    public static final CompilerConfigurationKey<JvmAbiStability> ABI_STABILITY =
+            CompilerConfigurationKey.create("ABI stability of class files produced by the JVM IR backend");
 
     public static final CompilerConfigurationKey<Boolean> DO_NOT_CLEAR_BINDING_CONTEXT =
             CompilerConfigurationKey.create("When using the IR backend, do not clear BindingContext between psi2ir and lowerings");

compiler/config.jvm/src/org/jetbrains/kotlin/config/JvmAbiStability.kt

@@ -0,0 +1,12 @@
+/*
+ * 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.config
+
+enum class JvmAbiStability(val description: String) {
+    STABLE("stable"),
+    UNSTABLE("unstable"),
+    ;
+}