Stream: add missing include for macOS builds

From the swift-corelibs-xctest CI:
```
swift-corelibs-foundation/CoreFoundation/Stream.subproj/CFStream.c:1686:5: error: call to undeclared function '_CFThreadSetName'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
    _CFThreadSetName(pthread_self(), "com.apple.CFStream.LegacyThread");
    ^
```

Author: compnerd

CoreFoundation/Stream.subproj/CFStream.c

@@ -13,6 +13,7 @@
 #include <string.h>
 #include "CFStreamInternal.h"
 #include "CFRuntime_Internal.h"
+#include "CFInternal.h"
 #include <stdio.h>
 #if TARGET_OS_WIN32
 #include <process.h>