Restore KotlinCompilerVersion.IS_PRE_RELEASE

This commit is a slightly modified revert of 4f29c113.
IS_PRE_RELEASE allows to make LATEST_STABLE version behave as
experimental when this flag is set to true.
The general goal is to prepare fix of KT-62058; after this commit
one can do it by changing IS_PRE_RELEASE flag to true.
The fix of KT-62058 is planned to be done during bootstrapping.
This preparation and the future fix are parts of umbrella KT-61951.

compiler/tests-common/tests/org/jetbrains/kotlin/checkers/CompilerTestLanguageVersionSettings.kt

@@ -37,7 +37,7 @@ data class CompilerTestLanguageVersionSettings(
     override fun getFeatureSupport(feature: LanguageFeature): LanguageFeature.State =
         extraLanguageFeatures[feature] ?: delegate.getFeatureSupport(feature)
 
-    override fun isPreRelease(): Boolean = false
+    override fun isPreRelease(): Boolean = KotlinCompilerVersion.isPreRelease()
 
     @Suppress("UNCHECKED_CAST")
     override fun <T> getFlag(flag: AnalysisFlag<T>): T = analysisFlags[flag] as T? ?: flag.defaultValue