Add tests for enhanced java signatures based on AbstractResolvedCallsTest.

Refactor AbstractResolvedCallsTest to support multiple carets (multiple methods being tested  for resolve) in testdata file.

compiler/testData/resolvedCalls/enhancedSignatures/map/mapMerge.kt

@@ -0,0 +1,21 @@
+fun valuesNotNull(map: MutableMap<Int, String>) {
+    map.<caret>merge(1, "x") { old, new -> old + new }
+}
+
+fun valuesNullable(map: MutableMap<Int, String?>) {
+    map.<caret>merge(1, "x") { old, new -> old + new }
+    map.<caret>merge(1, null) { old, new -> old + new }
+}
+
+fun <T> valuesT(map: MutableMap<Int, T>, newValue: T) {
+    map.<caret>merge(1, newValue) { old, new -> null }
+}
+
+fun <T : Any> valuesTNotNull(map: MutableMap<Int, T>, newValue: T) {
+    map.<caret>merge(1, newValue) { old, new -> null }
+}
+
+fun <T : Any> valuesTNullable(map: MutableMap<Int, T?>, newValue: T?) {
+    map.<caret>merge(1, newValue) { old, new -> new }
+    map.<caret>merge(1, newValue!!) { old, new -> new }
+}