[FE 1.0] Set a fixation priority for self type variables less than any of ready for fixation kinds

^KT-51040 Fixed
^KT-49838

compiler/testData/codegen/box/inference/kt51040.kt

@@ -0,0 +1,15 @@
+// WITH_STDLIB
+// FULL_JDK
+// TARGET_BACKEND: JVM
+
+import java.util.*
+
+inline fun <reified T : Enum<T>> emptyEnumSet(): EnumSet<T> = EnumSet.noneOf(T::class.java)
+fun <T : Enum<T>> enumSetOf(e: T): EnumSet<T> = EnumSet.of(e)
+
+enum class SomeEnum { ONE }
+val set = enumSetOf(SomeEnum.ONE).takeIf { it.size > 0 } ?: emptyEnumSet()
+
+fun box(): String {
+    return if (set.first() == SomeEnum.ONE) "OK" else "NOK"
+}

compiler/testData/codegen/box/sealed/kt49752.kt

@@ -1,6 +1,3 @@
-// IGNORE_BACKEND_FIR: JVM_IR
-// FIR status: several false UPPER_BOUND_VIOLATED are reported
-
 abstract class Interpreter<IS, TS, SELF>
         where IS : Interpreter.Intermediary<SELF>,
               TS : Interpreter.Terminal<SELF>,