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

unittests/Basic/DemangleTest.cpp

@@ -0,0 +1,13 @@
+#include "swift/Basic/DemangleWrappers.h"
+#include "gtest/gtest.h"
+
+using namespace swift::demangle_wrappers;
+
+TEST(Demangle, DemangleWrappers) {
+  EXPECT_EQ("", demangleSymbolAsString(""));
+  std::string MangledName = "_TtV1a1b\\\t\n\r\"\'\x1f\x20\x7e\x7f";
+  MangledName += '\0';
+  EXPECT_EQ("a.b with unmangled suffix \"\\\\\\t\\n\\r\\\"'\\x1F ~\\x7F\\0\"",
+      demangleSymbolAsString(MangledName));
+}
+