[FE 1.0] Eliminate resolution ambiguity with external type parameters

^KT-10926 Fixed

compiler/testData/diagnostics/tests/varargs/kt10926EnabledFeature.fir.kt

@@ -0,0 +1,12 @@
+// !LANGUAGE: +EliminateAmbiguitiesWithExternalTypeParameters
+// WITH_RUNTIME
+
+class AllCollection<T> {
+    fun <K, T> addAll(vararg values: T, values2: Array<K>) = "OK" // 1
+    fun <K, T> addAll(values: Array<K>, vararg values2: T) = 1 // 2
+}
+
+fun main(c: AllCollection<Any?>) {
+    // KT-49620
+    c.<!OVERLOAD_RESOLUTION_AMBIGUITY!>addAll<!>(arrayOf(""), values2 = arrayOf(""))
+}