Select most specific overloaded function/property by explicitly used arguments only.

Major rewrite of OverloadingConflictResolver.

compiler/testData/diagnostics/tests/resolve/overloadConflicts/varargsMixed.kt

@@ -0,0 +1,12 @@
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+
+object X1
+object X2
+
+fun overloadedFun5(vararg ss: String) = X1
+fun overloadedFun5(s: String, vararg ss: String) = X2
+
+val test1: X1 = <!OVERLOAD_RESOLUTION_AMBIGUITY!>overloadedFun5<!>("")
+val test2 = <!OVERLOAD_RESOLUTION_AMBIGUITY!>overloadedFun5<!>("", "")
+val test3: X2 = overloadedFun5(s = "", ss = "")
+val test4: X1 = overloadedFun5(ss = "")