Hide zlib and expat libs from the user of Poco libraries (replaces #4579) (#4724)

* foundation: Remove unused ucp.h

Nothing use this and it is not even included in Visual Studio project
files. Remove it so it will not confuse any more.

* foundation: Hide zlib from user

Hide zlib completly from user. This way we do not need to publish zlib.h
or zconfig.h.

As we now have two different pointer initalizing in constructor I choose
to use unique pointers so it is more obvious those are safe. I also
choose to use make_unique which default initalize z_stream_t. This makes
code more readable as we do not need to specifie every field of
z_stream_t. It really should not matter much if we initialize couple
field for nothing. If does we should add comment about that. Still
keeping _buffer without inializing as it is quite big.

* xml: Hide expat and ParserEngine from user

Hide expat completly from user. This way we do not need to publish
expat.h or expat_external.h.

I move also headers to orignal locations so diff is smaller compared to
original.

* chore(Foundation): Compression level constants

---------

Co-authored-by: Kari Argillander <kari.argillander@fidelix.com>

Foundation/include/Poco/InflatingStream.h

@@ -22,11 +22,8 @@
 #include "Poco/BufferedStreamBuf.h"
 #include <istream>
 #include <ostream>
-#if defined(POCO_UNBUNDLED)
-#include <zlib.h>
-#else
-#include "Poco/zlib.h"
-#endif
+
+struct z_stream_s;
 
 
 namespace Poco {
@@ -92,12 +89,12 @@ private:
 		INFLATE_BUFFER_SIZE = 32768
 	};
 
-	std::istream*  _pIstr;
-	std::ostream*  _pOstr;
-	char*    _buffer;
-	z_stream _zstr;
-	bool     _eof;
-	bool     _check;
+	std::istream*	_pIstr;
+	std::ostream*	_pOstr;
+	char*			_buffer;
+	z_stream_s*		_pZstr;
+	bool			_eof;
+	bool			_check;
 };