Checklist

• I added a descriptive title
• I searched open reports and couldn't find a duplicate

What happened?

The time needed for conda activate has gone up in the recent versions again.
We made some performance improvements for conda>=4.6 in gh-7122 and conda>=23.5 in gh-12550, but have quickly regressed on this in recent versions.

The following gives an overview of conda shell.posix activate run times and

• uses python=3.8 so we can compare over a wide range of conda versions,
• uses setuptools=58 for conda<=23.5 to factor out the impact of setuptools>=60's distutils injection,
• uses ruamel.yaml=0.16 since later versions got slower to import (tracking this upstream in https://sourceforge.net/p/ruamel-yaml/tickets/504/ ; already figured out the culprits/needed changes; will work with upstream to address this),
• has ruamel_yaml forcefully removed for the older conda versions to ensure the specified ruamel.yaml is used,

and was run on Linux 6.6.10, glibc 2.17, packages from conda-forge (apart from defaults::conda=24.1.0), with environments in memory on a tmpfs, and scaling governor/energy performance preference set to performance/performance on a 6 year old laptop with an i7-8550U.
(Running the same with powersave/powersave CPU settings causes times to rise upward of 200ms for the latest versions, i.e., very noticible delays.)

I've already prepared and tested the changes necessary to address those issues noted in the table above which have not already been covered by @jaimergp's work in gh-12550; I'll open a PR for this in the next few days.

Conda Info

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Conda Config

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Conda list

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Additional Context

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