FIR: Refine callable reference resolution in assignment position

synthetic_select<() -> T>(::foo) form allows to select better candidate
than synthetic_select(::foo) with expect type `() -> T`

compiler/testData/diagnostics/tests/j+k/sam/referenceToSamFunctionAgainstExpectedType.fir.kt

@@ -17,7 +17,7 @@ public class Inv<T> {
 // FILE: test.kt
 
 fun test(inv: Inv<String>) {
-    val m: ((String) -> String) -> Inv<String> = <!INITIALIZER_TYPE_MISMATCH!>inv::map<!>
+    val m: ((String) -> String) -> Inv<String> = inv::<!UNRESOLVED_REFERENCE!>map<!>
     <!INAPPLICABLE_CANDIDATE!>take<!>(inv::<!UNRESOLVED_REFERENCE!>map<!>)
 }