[js/web] fix nodejs detection (#16400)
### Description
We used to use `typeof fetch === 'undefined'` as condition to detect the
environment is Node.js or not. Before Node.js v18, this works. However,
in Node.js v18, it introduced `fetch` function, so this check does not
work any more.
This PR changes the condition to check whether `process`,
`process.versions` and `process.versions.node` exists.
Checking whether `process` exists is not enough. This is because in some
configuration, webpack may polyfill nodejs's process.
