cmip7repack: Repack CMIP7 netCDF-4 datasets

cmip7repack is a command-line tool for Unix-like platforms, bespoke to CMIP, which can be used by the modelling groups, prior to dataset publication, to "repack" their files (i.e. to re-organise the file contents to have a different chunk and internal file metadata layout) in such as way as to improve their read-performance over the lifetime of the CMIP7 archive (note that CMIP7 datasets are written only once, but read many times). check_cmip7_packing is a command-line tool for Unix-like platforms, bespoke to CMIP, which can be used to check if datasets have a sufficiently good internal structure. Any dataset that has been output by cmip7repack is guaranteed to pass the checks. Full details are available at https://github.com/NCAS-CMS/cmip7_repack, or with cmip7repack -h and check_cmip7_packing -h.