[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>

docs/developer/advanced/upgrading-nodejs.asciidoc

@@ -17,7 +17,7 @@ These files must be updated when upgrading Node.js:
   - {kib-repo}blob/{branch}/WORKSPACE.bazel[`WORKSPACE.bazel`] - The version is specified in the `node_version` property.
     Besides this property, the list of files under `node_repositories` must be updated along with their respective SHA256 hashes.
     These can be found on the https://nodejs.org[nodejs.org] website.
-    Example for Node.js v16.20.1: https://nodejs.org/dist/v16.20.1/SHASUMS256.txt.asc
+    Example for Node.js v18.17.0: https://nodejs.org/dist/v18.17.0/SHASUMS256.txt.asc
 
 See PR {kib-repo}pull/128123[#128123] for an example of how the Node.js version has been upgraded previously.
 
@@ -30,6 +30,13 @@ When upgrading to a new major version of Node.js, the following extra steps must
     You can change which Node.js major version to view, by changing the selected branch.
     If Node.js has dropped support for platform still supported by Kibana, appropriate steps must be taken as soon as possible to deprecate support for this platform. This way support for it can be dropped before the currently used major version of Node.js https://github.com/nodejs/release#release-schedule[reaches End-of-Life].
 
+[[custom-nodejs-builds]]
+=== Custom builds of Node.js
+
+Due to Node.js 16 coming to an https://nodejs.org/en/blog/announcements/nodejs16-eol[early End-of-Life] and Node.js 18 no longer supporting the same platforms that {kib} supports (most notably CentOS7/RHEL7), we cannot bundle the official Node.js binaries with the Linux distributable of {kib}.
+To keep support for these older platforms, we're bundling the Linux distributable of {kib} with a https://github.com/elastic/kibana-custom-nodejs-builds[custom build of Node.js] with extended backwards compatibility.
+The only difference between the offical Node.js build and our custom build, is the version of `glibc` that it's compiled against.
+
 === Backporting
 
 The following rules are not set in stone.