[Ops] Bump Node.js to version 18 (#160289)

## Summary

Bumps node.js to 18.17.0 (replacement for PR #144012 which was later
reverted)

As a result, these categorical additions were needed: 
- `node` evocations will need the `--openssl-legacy-provider` flag,
wherever it would use certain crypto functionalities
- tests required updating of the expected HTTPS Agent call arguments,
`noDelay` seems to be a default
 - `window.[NAME]` fields cannot be written directly
 - some stricter typechecks

This is using our in-house built node.js 18 versions through the URLs
the proxy-cache. (built with
https://github.com/elastic/kibana-custom-nodejs-builds/pull/4)

These urls are served from a bucket, where the RHEL7/Centos7 compatible
node distributables are. (see:
https://github.com/elastic/kibana-ci-proxy-cache/pull/7)

Further todos: 
 - [x] check docs wording and consistency
 - [ ] update the dependency report
 - [x] explain custom builds in documentation
 - [x] node_sass prebuilts

---------

Co-authored-by: Kibana Machine <42973632+kibanamachine@users.noreply.github.com>
Co-authored-by: Tiago Costa <tiago.costa@elastic.co>
Co-authored-by: Thomas Watson <w@tson.dk>

.node-version

@@ -1 +1 @@
-16.20.1
+18.17.0