archivers/zstd: Clean up 72ad532057c9f9fb6fa370c80f663c005e9dd021

• Use WRKSRC instead of BUILD_WRKSRC
• Use SUB_FILES/SUB_LIST instead of a bunch of REINPLACE_CMD
• Use FILESDIR instead of PATCHDIR
• Clean up files/*:
  • Remove unnecessary file: zstdConfig.cmake is already in the source tarball
  • Rename patch file: Remove unnecessary .in suffix