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/position.h

@@ -21,14 +21,13 @@
 
 #include <cassert>
 #include <deque>
-#include <memory> // For std::unique_ptr
+#include <iosfwd>
+#include <memory>
 #include <string>
 
 #include "bitboard.h"
-#include "evaluate.h"
-#include "types.h"
-
 #include "nnue/nnue_accumulator.h"
+#include "types.h"
 
 namespace Stockfish {