[FIR] fix false negative MUST_BE_INITIALIZED for deferred init + custom setter case

^KT-58346 Fixed
Review: https://jetbrains.team/p/kt/reviews/9967

BTW this commit accidentaly and partially fixes KT-57553 for K2, because
of a cleaner K2 architecture. I will unify MUST_BE_INITIALIZED behaviour
in K1 and K2 in the next commits

compiler/testData/ir/irText/classes/initVar.kt

@@ -16,24 +16,3 @@ class TestInitVarWithCustomSetter {
     var x = 0
         set(value) { field = value }
 }
-
-class TestInitVarWithCustomSetterWithExplicitCtor {
-    var x: Int
-        set(value) { field = value }
-
-    init {
-        x = 0
-    }
-
-    constructor()
-}
-
-class TestInitVarWithCustomSetterInCtor {
-    var x: Int set(value) {
-        field = value
-    }
-
-    constructor() {
-        x = 42
-    }
-}