[Core API] Introduce useTypeRefinement analysis flag

compiler/frontend/src/org/jetbrains/kotlin/config/AnalysisFlags.kt

@@ -32,4 +32,7 @@ object AnalysisFlags {
 
     @JvmStatic
     val constraintSystemForOverloadResolution by AnalysisFlag.Delegates.ConstraintSystemForOverloadResolution
+
+    @JvmStatic
+    val useTypeRefinement by AnalysisFlag.Delegates.Boolean
 }

compiler/frontend/src/org/jetbrains/kotlin/config/KotlinTypeRefinerImpl.kt

@@ -139,6 +139,9 @@ class KotlinTypeRefinerImpl(
     }
 }
 
+val LanguageVersionSettings.isTypeRefinementEnabled: Boolean
+    get() = getFlag(AnalysisFlags.useTypeRefinement)
+
 private val TypeConstructor.allDependentTypeConstructors: Collection<TypeConstructor>
     get() = when (this) {
         is NewCapturedTypeConstructor -> {