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/optionalOf.kt

@@ -0,0 +1,9 @@
+import java.util.*
+
+fun use() {
+    val x: String? = "x"
+    Optional.<caret>of(x)
+
+    Optional.<caret>of(x!!)
+    Optional.<caret>ofNullable(x)
+}