`json-dat.py` script is hard to use with new pip restrictions

[sgpthomas]

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The new pip restrictions force you to install everything in a virtualenv. This makes it very annoying to run fud/fud2 commands that rely on this without resorting to disabling this error, or making new virtualenvs. Both of these seem non-ideal. I think probably the solution is to turn json-dat.py into an installable python package, but I'm open to ideas. The other reasonable possibility that I can imagine is to remove all python dependencies except the fud dependency. And then set PYTHONPATH to include the fud directory when we run json-dat.py.

[sgpthomas]

I think a better solution is to set the python var in fud2.toml to a venv python with the correct things installed. This is putting some of the burden on plugin writers to not use python directly, and instead read the python version from the config. Which I think most of them do already.

[rachitnigam]

#2404 might help solve this

[EclecticGriffin]

#2480 automatically sets the python var in the fud2 configs to an appropriate venv. So I believe this is also resolved