Cleanup includes

Reorder a few includes, include "position.h" where it was previously missing
and apply include-what-you-use suggestions. Also make the order of the includes
consistent, in the following way:

1. Related header (for .cpp files)
2. A blank line
3. C/C++ headers
4. A blank line
5. All other header files

closes https://github.com/official-stockfish/Stockfish/pull/4763
fixes https://github.com/official-stockfish/Stockfish/issues/4707

No functional change

src/tt.h

@@ -19,6 +19,9 @@
 #ifndef TT_H_INCLUDED
 #define TT_H_INCLUDED
 
+#include <cstddef>
+#include <cstdint>
+
 #include "misc.h"
 #include "types.h"