[FIR] Generate signatures for synthesized class delegation fields

This is to align the behavior with K1.

^KT-57754 Fixed

Co-authored-by: Alexander Udalov <alexander.udalov@jetbrains.com>

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

@@ -1,6 +1,3 @@
-// MUTE_SIGNATURE_COMPARISON_K2: ANY
-// ^ KT-57754
-
 interface IFooBar {
     fun foo()
     fun bar()