[gardening] Standardize ./unittests/Basic so that all tests have the Test.cpp suffix.

unittests/Basic/UnicodeTest.cpp

@@ -0,0 +1,15 @@
+#include "swift/Basic/Unicode.h"
+#include "gtest/gtest.h"
+
+using namespace swift::unicode;
+
+TEST(ExtractExtendedGraphemeCluster, Test1) {
+  EXPECT_EQ("", extractFirstExtendedGraphemeCluster(""));
+  EXPECT_EQ("a", extractFirstExtendedGraphemeCluster("a"));
+  EXPECT_EQ("a", extractFirstExtendedGraphemeCluster("abc"));
+}
+
+TEST(IsSingleExtendedGraphemeCluster, Test1) {
+  EXPECT_EQ(false, isSingleExtendedGraphemeCluster(""));
+  EXPECT_EQ(true, isSingleExtendedGraphemeCluster("a"));
+}