Fixes #37819 - Remove @theforeman/builder usage

[MariaAga]

Moving it into foreman from foreman-js.
I saw it being used in some plugins and I think it can be removed from them, if they run npm test and webpack compilation goes without errors for them (for example: REX).
Other plugins can stop using builder as well and import from core directly, for example, in Katello:

const { foremanLocation } = require('@theforeman/find-foreman');

module.exports = {
  presets: [foremanLocation()+'/webpack/babel'],
};

[ekohl]

In other places we always use __dirname. I'd prefer it if we were consistent and didn't rely on the current working directory too much. Perhaps we need a new const project_root = path.join(__dirname, '..') that can then be used everywhere.

[MariaAga]

Need to fix the imports yeah, thanks!

[MariaAga]

@theforeman/packaging I'm assuming theforeman/foreman-packaging#11257 will make rpm-build happy?