[ENH] - Remove ability to easily install python packages globally in pip

[costrouc]

Feature description

Set the environment variable PIP_REQUIRE_VIRTUALENV=true to prevent global pip installs of packages.

I tried this within a docker container and this is the error messages that users would get

$ docker run -it python bash
root@f5040281fa1e:/# export PIP_REQUIRE_VIRTUALENV=true
root@f5040281fa1e:/# pip install numpy
ERROR: Could not find an activated virtualenv (required).

Value and/or benefit

We want to prevent users from easily installing within $HOME/.local in nebari. Since this breaks environments often.

Anything else?

No response

[dharhas]

How do we deal with development packages? i.e. things we currently install with pip install -e .

[kcpevey]

Resolved by #2191