Refactor AbstractMultiFileJvmBasicCompletionTest to extend CompletionTestCase

Extract common code from JetFixtureCompletionBaseTestCase to CompletionTestUtil.kt
Reason for this change is that I couldn't get the check that prohibits tree loading to work with fixture test case

idea/testData/completion/basic/multifile/InImportedFunctionLiteralParameter/InImportedFunctionLiteralParameter.dependency.kt

@@ -0,0 +1,9 @@
+package second
+
+class Some {
+  // Two function to prevent automatic insert
+  fun testFunction1() : Int = 12
+  fun testFunction2() : Int = 12
+}
+
+fun someWithLiteral(body: (Some) -> Unit): Int = 12

idea/testData/completion/basic/multifile/InImportedFunctionLiteralParameter/InImportedFunctionLiteralParameter.kt

@@ -0,0 +1,11 @@
+package first
+
+// For KT-3096 No completion in function literal
+
+import second.someWithLiteral
+
+fun test() {
+  someWithLiteral({file -> file.testFu<caret>})
+}
+
+// EXIST: testFunction1, testFunction2