add clang-format

This introduces clang-format to enforce a consistent code style for Stockfish.

Having a documented and consistent style across the code will make contributing easier
for new developers, and will make larger changes to the codebase easier to make.

To facilitate formatting, this PR includes a Makefile target (`make format`) to format the code,
this requires clang-format (version 17 currently) to be installed locally.

Installing clang-format is straightforward on most OS and distros
(e.g. with https://apt.llvm.org/, brew install clang-format, etc), as this is part of quite commonly
used suite of tools and compilers (llvm / clang).

Additionally, a CI action is present that will verify if the code requires formatting,
and comment on the PR as needed. Initially, correct formatting is not required, it will be
done by maintainers as part of the merge or in later commits, but obviously this is encouraged.

fixes https://github.com/official-stockfish/Stockfish/issues/3608
closes https://github.com/official-stockfish/Stockfish/pull/4790

Co-Authored-By: Joost VandeVondele <Joost.VandeVondele@gmail.com>

src/nnue/evaluate_nnue.h

@@ -32,48 +32,48 @@
 #include "nnue_feature_transformer.h"
 
 namespace Stockfish {
-  class Position;
-  enum Value : int;
+class Position;
+enum Value : int;
 }
 
 namespace Stockfish::Eval::NNUE {
 
-  // Hash value of evaluation function structure
-  constexpr std::uint32_t HashValue =
-      FeatureTransformer::get_hash_value() ^ Network::get_hash_value();
+// Hash value of evaluation function structure
+constexpr std::uint32_t HashValue =
+  FeatureTransformer::get_hash_value() ^ Network::get_hash_value();
 
 
-  // Deleter for automating release of memory area
-  template <typename T>
-  struct AlignedDeleter {
+// Deleter for automating release of memory area
+template<typename T>
+struct AlignedDeleter {
     void operator()(T* ptr) const {
-      ptr->~T();
-      std_aligned_free(ptr);
+        ptr->~T();
+        std_aligned_free(ptr);
     }
-  };
+};
 
-  template <typename T>
-  struct LargePageDeleter {
+template<typename T>
+struct LargePageDeleter {
     void operator()(T* ptr) const {
-      ptr->~T();
-      aligned_large_pages_free(ptr);
+        ptr->~T();
+        aligned_large_pages_free(ptr);
     }
-  };
+};
 
-  template <typename T>
-  using AlignedPtr = std::unique_ptr<T, AlignedDeleter<T>>;
+template<typename T>
+using AlignedPtr = std::unique_ptr<T, AlignedDeleter<T>>;
 
-  template <typename T>
-  using LargePagePtr = std::unique_ptr<T, LargePageDeleter<T>>;
+template<typename T>
+using LargePagePtr = std::unique_ptr<T, LargePageDeleter<T>>;
 
-  std::string trace(Position& pos);
-  Value evaluate(const Position& pos, bool adjusted = false, int* complexity = nullptr);
-  void hint_common_parent_position(const Position& pos);
+std::string trace(Position& pos);
+Value       evaluate(const Position& pos, bool adjusted = false, int* complexity = nullptr);
+void        hint_common_parent_position(const Position& pos);
 
-  bool load_eval(std::string name, std::istream& stream);
-  bool save_eval(std::ostream& stream);
-  bool save_eval(const std::optional<std::string>& filename);
+bool load_eval(std::string name, std::istream& stream);
+bool save_eval(std::ostream& stream);
+bool save_eval(const std::optional<std::string>& filename);
 
 }  // namespace Stockfish::Eval::NNUE
 
-#endif // #ifndef NNUE_EVALUATE_NNUE_H_INCLUDED
+#endif  // #ifndef NNUE_EVALUATE_NNUE_H_INCLUDED