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/optional/optionalEmpty.kt

@@ -0,0 +1,6 @@
+import java.util.*
+
+fun use() {
+    Optional.<caret>empty<String>()
+    Optional.<caret>empty<String?>()
+}