We're currently calling `XXH3_createState` and `XXH3_freeState` when hashing an object. However, it may be slow because they call `malloc` and `free`, which may affect the performance. This change avoids the use of the streaming API as much as possible by using an internal buffer.
The codebase is filled with includes that are unused, and which thus can be removed. At the same time, the files often do not include all headers that contain the definitions used in those files. This change uses clang-format and clang-tidy to clean up the includes, with minor manual intervention to ensure the code compiles on all platforms.
