PR: Add condabin directory, relative to sys.executable and provided pyexec, to paths searched for conda executable

[mrclary]

Description of Changes

For the cases where conda environments are in non-standard locations, including possibly Spyder's runtime environment for conda installations, a conda executable may not be found.
This PR adds condabin directories, relative to Spyder's runtime executable and an optional Python executable, to the paths searched.

Optional extra search paths are added to is_program_installed.

Issue(s) Resolved

Part of #20357.

Affirmation

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[ccordoba12]

I think this is missing a test because it's an important functionality. For that I suggest to temporarily remove CONDA_EXE from os.environ and run find_conda(pyexec=sys.executable) to see if we're actually able to find it.

[pep8speaks]

Hello @mrclary! Thanks for updating this PR. We checked the lines you've touched for PEP 8 issues, and found:

There are currently no PEP 8 issues detected in this Pull Request. Cheers! 🍻

Comment last updated at 2024-03-05 15:41:05 UTC

[ccordoba12]

On the good news front, I'd like to make a quick comment to say that I tested the Linux installer from this PR and it solves the problem of dead consoles in it.

[ccordoba12]

Looks good to me now, thanks @mrclary!