FIR serializer: consider exotic types as errors (breaks 4 BB tests)

compiler/testData/codegen/box/diagnostics/functions/inference/kt6176.kt

@@ -1,3 +1,4 @@
+// IGNORE_BACKEND_FIR: JVM_IR
 // !DIAGNOSTICS: -DEBUG_INFO_SMARTCAST
 
 fun <R> foo(f: () -> R): R = f()

compiler/testData/codegen/box/javaInterop/notNullAssertions/enhancedNullability/inFunctionWithExpressionBodyWithJavaGeneric.kt

@@ -1,3 +1,4 @@
+// IGNORE_BACKEND_FIR: JVM_IR
 // !LANGUAGE: +StrictJavaNullabilityAssertions
 // TARGET_BACKEND: JVM
 // SKIP_JDK6

compiler/testData/codegen/box/lazyCodegen/ifElse.kt

@@ -1,3 +1,4 @@
+// IGNORE_BACKEND_FIR: JVM_IR
 class A (val p: String, p1: String, p2: String) {
 
     var cond1 :String = ""

compiler/testData/codegen/box/regressions/commonSupertypeContravariant2.kt

@@ -1,3 +1,4 @@
+// IGNORE_BACKEND_FIR: JVM_IR
 interface In<in E>
 class A : In<A>
 class B : In<B>