JVM_IR KT-43877 fix generic signatures for SAM-converted lambdas

compiler/testData/codegen/bytecodeListing/sam/callableRefGenericFunInterface.kt

@@ -0,0 +1,12 @@
+// WITH_SIGNATURES
+// FILE: t.kt
+
+fun interface Sam<T> {
+    fun get(): T
+}
+
+fun <T> expectsSam(sam: Sam<T>) = sam.get()
+
+fun <T> foo(): T = null!!
+
+fun <T> genericSam(): T = expectsSam(::foo)