Move testable IS_PRE_RELEASE flag to KotlinCompilerVersion

It'll be used in the JS back-end as well soon, so
DeserializedDescriptorResolver is not the best place for it

core/descriptor.loader.java/src/org/jetbrains/kotlin/load/kotlin/DeserializedDescriptorResolver.kt

@@ -75,7 +75,7 @@ class DeserializedDescriptorResolver {
 
     private val KotlinJvmBinaryClass.isPreReleaseInvisible: Boolean
         get() = !JvmMetadataVersion.skipCheck &&
-                !IS_PRE_RELEASE &&
+                !KotlinCompilerVersion.isPreRelease() &&
                 (classHeader.isPreRelease || classHeader.metadataVersion == KOTLIN_1_1_EAP_METADATA_VERSION)
 
     internal fun readData(kotlinClass: KotlinJvmBinaryClass, expectedKinds: Set<KotlinClassHeader.Kind>): Array<String>? {
@@ -108,14 +108,5 @@ class DeserializedDescriptorResolver {
                 setOf(KotlinClassHeader.Kind.FILE_FACADE, KotlinClassHeader.Kind.MULTIFILE_CLASS_PART)
 
         private val KOTLIN_1_1_EAP_METADATA_VERSION = JvmMetadataVersion(1, 1, 2)
-
-        var IS_PRE_RELEASE = KotlinCompilerVersion.IS_PRE_RELEASE
-            get() {
-                val testOverrideValue = System.getProperty(TEST_IS_PRE_RELEASE_SYSTEM_PROPERTY)
-                return testOverrideValue?.toBoolean() ?: field
-            }
-            @Deprecated("Should only be used in tests") set
-
-        const val TEST_IS_PRE_RELEASE_SYSTEM_PROPERTY = "kotlin.test.is.pre.release"
     }
 }