Provide a --target option on uninstall (to undo install with --target)

[ronpandolfi]

What's the problem this feature will solve?
Currently, there is no clear way to uninstall a package that has been installed to a directory outside sys.prefix using pip install --target. Attempting to do so via modifying sys.path results in "Not uninstalling X at Y, outside environment Z"

Describe the solution you'd like
Mirror the functionality of pip install --target to pip uninstall --target

This would enable installing/uninstalling packages to sandboxed directories (similarto a venv, but without the extra baggage), as --target seems to be intended.

Alternative Solutions
While a venv could provide an alternative solution, it is still an issue that there is no 'undo' for the situation where --target is used.

[chrahunt]

Related to #4575.

[xeacott]

Is this specific feature going to be added?

[pfmoore]

As the label says, discussion is needed (and the linked issue gives some background). So not immediately is probably the best answer - we will quite probably implement something addressing the more general need at some point, though.

[GitHunter0]

It is an important matter. Is there an workaround for that?

[ccx1997]

I finally got it by adding python -m.

conda activate env_path
python -m pip uninstall <package_name>