Remove unused packages from analysis3

[aidanheerdegen]

yamanifest can be removed. It is used by payu which has also been removed from the analysis3 environment.

nchash can both be removed. It is a fast change detection hash I wrote to use with yamanifest.

dusqlpg is part of the disk usage tracking @ScottWales wrote, and is no longer used.

doit was used in the automated resource tracking. We're using it internally at ACCESS-NRI, but not with this conda environment, so it can also be deleted I think.

splitvar is a utility I wrote to split netCDF files by variable and time to be "CMIP like". I used it for some processing of ocean model output, but that is no longer required, and I'd suggest removing it as I don't believe it is used.

addmeta is a utility I wrote years ago as a proof-of-concept tool for systematic application of meta-data updates. It isn't being used and should be removed from the environment.