CI: Update NPM, Python, fix 'nvm use'
Several of the repo dependencies don't support NPM releases before v16. Several of them have also dropped support for Python 2.
This MR updates the CI setup commands to:
- use
nvm install --lts v16
to install the current LTS release of Node 16 - Run
nvm use v16
with the--delete-prefix
flag added, as apparently that's always needed now - Install Python 3 from
apt
, instead of the EOL'dpython2