FIR: Fix overload resolution for some invoke cases

Namely, it's about the cases when there are multiple variable candidates
with the same priority and all of them should be collected and compared

compiler/fir/analysis-tests/testData/resolveWithStdlib/problems/invokePriority.kt

@@ -29,6 +29,6 @@ class E {
 }
 
 fun main() {
-    E.f() // Resolves to (2) in old FE (to (1) in FIR with object implicit invoke support)
+    E.<!AMBIGUITY!>f<!>() // Resolves to (2) in old FE (ambiguity in FIR)
     E.f.invoke() // Resolves to (1)
-}
+}

compiler/fir/analysis-tests/testData/resolveWithStdlib/problems/invokePriority.txt

@@ -74,6 +74,6 @@ FILE: invokePriority.kt
 
     }
     public final fun main(): R|kotlin/Unit| {
-        Q|E|.R|/E.Companion.f|.R|/E.f.invoke|()
+        Q|E|.<Ambiguity: f, [/E.f.invoke, kotlin/Function0.invoke]>#()
         Q|E.f|.R|/E.f.invoke|()
     }