Add repoquery showneeds and depends

[JeanChristopheMorinPerso]

Checklist

• [x] I added a descriptive title
• [x] I searched open requests and couldn't find a duplicate

What is the idea?

Now that https://github.com/conda/rattler/issues/518 is complete, the only missing pieces are the whoneeds and the requires subcommands.

$ conda repoquery --help
usage: conda repoquery [-h] {whoneeds,depends,search} ...

Advanced search for repodata.

positional arguments:
  {whoneeds,depends,search}
    whoneeds            Show packages that depend on this package.
    depends             Show dependencies of this package.
    search              Show all available package versions.

options:
  -h, --help            Show this help message and exit.

Why is this needed?

I don't know if these commands are widely used, but they can be useful.

What should happen?

No response

Additional Context

No response

[baszalmstra]

Would you be able to share the api you would like to see for this?

Happy to work on implementing this.

[JeanChristopheMorinPerso]

I never really used the API for that, so I'm not too sure what kind of API would be needed.

[baszalmstra]

@jaimergp Do you have thoughts maybe?