Allow `conda self install` to accept a `--channel` argument

[ForgottenProgramme]

Checklist

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As of now conda self install not accept a -c/--channel argument.
Would we like to add that capability?
Let's use this issue's comment section to discuss and decide.

What is the idea?

conda self install accepts a --channel argument so that users can decide which channel to install the conda plugin from.

Why is this needed?

Giving users more freedom to choose where their plugin comes from

What should happen?

conda self install can be run with --channel flag

Additional Context

No response

[marcoesters]

I think it's safer to not allow mixing channels. If a user really wants to, they should be using --override-frozen instead. Allowing channel mixing is an antipattern and contradicts standard advice to not mix defaults with conda-forge.