This script is only used for the github e2e tests so doesn't need to be
inside /bin

Just removing some unused/unnecessary scripts and `IS_BETA` env variable
+ the associated code (we don't use this in the OS version of Actual).

After #1115, new Node.js versions will be able to be used for
development of the frontend. This PR changes the recommended Node.js
version to 18 (the current LTS version). I have also tested with 16 and
20 and it works.

I also took the opportunity to:

- move the build script that was at the project root to the `bin/`
folder
- update the `browserslist` to target Electron 24 (which is the version
we currently build against). This results in a slightly smaller bundle
due to no longer having to transpile optional chaining.

Updates to the latest version of electron and moves the backend-frontend
communication from node-ipc to websockets. This resolves the previous
roadblock regarding `nodeIntegration` .

Done

- Remove node-ipc in favour of websockets. 
- Move file copying out of `preload.js` to avoid importing module `fs`
there
- Bump all electron pacakge versions to the latest
- Added new package for finding open ports as node-ipc is gone
- Tweaked webpack config for above changes


Partially fixes #468

Questions/ Pending:
- Literally every single test fails for me, presumably some issue with
my setup/environment.
- The websocket communication is not using TLS. I'm not sure how to
enable this, or if we even need to as its all local.
- Still need to create the CI for building/deploying but I'm not sure
where start in this regard as i have no exp with it. Presumably we will
need to point the electron auto-updater to the github releases url's. If
people are happy with this PR I will look at adding the CI before its
merged.
- In dev mode only, I have disabled TLS security becuase my docker
container's cert is not signed. I _assume_ this will be true for other
people who spin up the server on thier own hardware. Perhaps I just need
to change my cert to one from letsencrypt or something...

Notes.
I have not touched javascript in eons so my apologies if the commit
trail is a bit fragmented. I tried to keep them fairly contained and
then there is a slightly gnarly final commit fixing all the linter
issues... Please let me know if you want me to squash some commits etc.

I initially tried to move this to web workers the same way the web app
does it but this was unsuccessful. I have found no way to spin up a
worker in one place (frontend/backend) and then pass this worker to the
other. The electron ipc channels don't allow you to directly pass
objects such as workers, everything is cloned/serialised. Passing a port
number so the other end can spin up its own socket works fine.

---------

Co-authored-by: Shazib Hussain <contact@shazib.com>
Co-authored-by: Jed Fox <git@jedfox.com>