FIR: support DefinitelyNotNull types

#KT-49465 Fixed

compiler/testData/codegen/box/casts/castToDefinitelyNotNullType.kt

@@ -3,8 +3,6 @@
 // IGNORE_BACKEND: JS_IR
 // IGNORE_BACKEND: WASM
 // IGNORE_BACKEND: NATIVE
-// IGNORE_BACKEND_FIR: JVM_IR
-// FIR status: Syntax error at (T & Any)
 
 fun <T> test(t: T) = t as (T & Any)
 

compiler/testData/codegen/box/notNullAssertions/definitelyNotNullTypes.kt

@@ -1,7 +1,5 @@
 // !LANGUAGE: +DefinitelyNonNullableTypes +ProhibitUsingNullableTypeParameterAgainstNotNullAnnotated
 // TARGET_BACKEND: JVM
-// IGNORE_BACKEND_FIR: JVM_IR
-// FIR status: wrong NOTHING_TO_OVERRIDE at KDerived.foo
 // FILE: JClass.java
 
 import org.jetbrains.annotations.*;