investigate removal of `node_env` script on ansible-provisioned nodes

Task:

• investigate removal of `node_env` script on ansible-provisioned nodes
• is it safe to remove support for multiple versions of node, now that theia is gone?
• can we switch to a simple rpm-installed npm?
• are the variables in job-config.json related to node/npm/yarn version still used/relevant?

See:

• https://gitlab.cee.redhat.com/codeready-workspaces/ansible-scripts/-/blob/master/roles/nodejs/tasks/env.yml#L22-33
• https://gitlab.cee.redhat.com/codeready-workspaces/crw-jenkins/-/merge_requests/1557/diffs (another way to install & use npm)

Note that dsc_3.x builds use node differently too:

# default node version
. ~/node_env ''' + DS_VERSION + ''' 
# special node version for dsc only
nvm install ''' + nodeVersion + '''; . $HOME/.nvm/nvm.sh; nvm use ''' + nodeVersion + '''
echo "Node: $(node --version) ( $(which node) )"
echo "Yarn: $(yarn --version) ( $(which yarn) )"