Fir2Ir: enable IR-based fake override builder

Invert the logic of IR/FIR2IR-based generators: change the CLI argument
to -Xuse-fir-fake-override-builder, test directive to
USE_FIR_BASED_FAKE_OVERRIDE_GENERATOR, etc.

The changes in test data caused by using IR fake override builder by
default are in the subsequent commit.

 #KT-61514

compiler/testData/ir/irText/declarations/kt65432.kt

@@ -1,10 +1,7 @@
-// WITH_STDLIB
-// ENABLE_IR_FAKE_OVERRIDE_GENERATION
-// SEPARATE_SIGNATURE_DUMP_FOR_K2
-// ^ Value parameters in fake overrides generated by K1 and K2 are different
-
 // WITH_REFLECT
 // TARGET_BACKEND: JVM_IR
+// SEPARATE_SIGNATURE_DUMP_FOR_K2
+// ^ Value parameters in fake overrides generated by K1 and K2 are different
 
 // FILE: Java1.java
 public class Java1 extends KotlinClass { }
@@ -14,4 +11,4 @@ import java.util.ArrayList
 
 class A : Java1()
 
-open class KotlinClass : ArrayList<Int>()
+open class KotlinClass : ArrayList<Int>()