Update .tool-versions and .nvmrc to use nodejs v20.12.2
What does this MR do and why?
This is needed in preparation of updating nodejs from 18.17 to 20.12 since the former is nearing end-of-life. In addition, the updates to npm and its node-gyp dependencies will fix support for Python 3.12.
Relates to gitlab-development-kit#2081 (closed)
Edited by Stan Hu