[FIR2IR] Properly create FIR f/o for lazy IR f/o

```kotlin
interface A {
    fun foo() // (1)
}

interface B : A {
    // f/o fun foo() // (2)
}
```

In previous commits it was forgotten to create new FIR declarations for
  IR fake-overrides, which led to the situation when `IR lazy functions
  of `(1)` and `(2)` both contained fir of function (1) as their base
  declaration

It seems this change fixed some cases from KT-42020

compiler/testData/codegen/box/compileKotlinAgainstKotlin/clashingFakeOverrideSignatures.kt

@@ -1,7 +1,8 @@
-// IGNORE_BACKEND_K2: JVM_IR, JS_IR
-// KT-59609
+// IGNORE_BACKEND_K2: JS_IR
 // IGNORE_BACKEND: NATIVE
-// FIR status: Validation failed. TODO decide if we want to fix KT-42020 for FIR as well
+// IGNORE_CODEGEN_WITH_IR_FAKE_OVERRIDE_GENERATION
+// Reason: KT-42020
+
 // MODULE: lib
 // FILE: a.kt
 package a