Consistent Integer Types

example of using, to avoid mixed usage of std::uint/std::int and uint/int...
```cpp
using u64 = std::uint64_t;
using u32 = std::uint32_t;
using u16 = std::uint16_t;
using u8  = std::uint8_t;

using i64 = std::int64_t;
using i32 = std::int32_t;
using i16 = std::int16_t;
using i8  = std::int8_t;

using usize = std::size_t;
using isize = std::ptrdiff_t;

#if defined(__GNUC__) && defined(IS_64BIT)
__extension__ using u128 = unsigned __int128;
__extension__ using i128 = signed __int128;
#endif
```

closes https://github.com/official-stockfish/Stockfish/pull/6874

No functional change

src/attacks.h

@@ -81,7 +81,7 @@ struct DualMagic {
     // Precomputed 2 * square_bb(sq), 2 * reverse(square_bb(sq))
     Bitboard r, rr;
 
-    const uint8_t* RESTRICT rankAttacksLookup;
+    const u8* RESTRICT rankAttacksLookup;
     // 8 * rank_of(sq)
     int shift;
 
@@ -130,8 +130,8 @@ const DualMagic& dual_magic(Square s);
 struct Magic {
     Bitboard mask;
     #ifdef USE_PEXT
-    uint16_t* attacks;
-    Bitboard  pseudoAttacks;
+    u16*     attacks;
+    Bitboard pseudoAttacks;
     #else
     Bitboard* attacks;
     Bitboard  magic;