lint_setup should not require elevated privileges (#61798)
Summary:
s/pip/pip3/ (because unversioned pip can reference either pip2 or pip3
depending on setup)
Always invoke `pip install` with user option (otherwise, unless one is
using conda environment, it will try to install in system folder, which
should not be writable to regular users)
Do not install shellcheck in `/usr/bin`, but rather rely on `~/.local/bin` and add it to the PATH
Pull Request resolved: https://github.com/pytorch/pytorch/pull/61798
Reviewed By: zhouzhuojie, seemethere
Differential Revision: D29747286
Pulled By: malfet
fbshipit-source-id: 30cb51fe60b5096b758f430d1c51465205532a19
