Add support for SHA256 hashes in explicit files

[jaimergp]

Description

• Comes from Write specification for text spec input files ceps#79 (comment)
• Closes Feature request: conda env create/export with sha256 (sha256 in conda list --explicit) #7882
• Closes More checksums options with packages #2903 (added in 2016!)

I tried to make it backwards compatible, but older conda versions will fail with a SHA256. Hopefully the error message is easy to find so I'll mention it in the news file so Google takes folks the right place. Also here for good measure:

If you find an error like this:

conda.exceptions.ParseError: Could not parse explicit URL: https://conda.anaconda.org/conda-forge/linux-aarch64/ca-certificates-2024.7.4-hcefe29a_0.conda#562bfc2608d82996a08e5b5b2366ed319a51ace6a2518a004ba672edca75fc23

You presumably need to update conda to the latest version (>=24.9.0), which does have support for the 64-char long SHA256 hashes. I also added a created-by: comment to point out which tool and version generated the tool. Thought of adding something like txtfile-version or so on, but that'll require a bigger refactor if we want to utilize it.

Checklist - did you ...

• Add a file to the news directory (using the template) for the next release's release notes?
• Add / update necessary tests?
• Add / update outdated documentation?

[codspeed-hq]

CodSpeed Performance Report

Merging #14048 will not alter performance

_{Comparing jaimergp:support-explicit-sha256 (523d29b) with main (3a1ed8e)}

Summary

✅ 21 untouched benchmarks

[dholth]

I like it