cc@Rogdham (can't request review).

Best reviewed commit-by-commit.

This contains several clean-ups for the_zstd module.

• _compressionLevel_values is replaced with a single int constant, the default compression level
• zstd_version_info is initialised from the macros, removing version decomposition arithmetic
• remove the unused_ZSTD_CStreamSizes
• Replace_ZSTD_DStreamSizes withZSTD_DStreamOutSize
• Remove unused_ZSTD_Config
• Remove zstd version string from error messages -- it is inconsistently used, and the version can be found from the module-level variables
• small refactoring ofset_zstd_error()
• Inline theadd_parameters function and use the existingPyModule_AddIntMacro rather than defining a local equivalent
• Remove the leading underscore from several constants in an already private module, use an explicit list of names for the re-exporting incompression.zstd

A

• Issue:Implement PEP 784 - Adding Zstandard to the Python standard library #132983