Only install the required dependencies for chromium/firefox and nothing more.
We get the rest via playwright.

this makes it easier to debug CI things locally

The behaviour should be the same, except the deployer command
is now independent of the CWD.

We also no longer ship deployer in the docker image, but install
it via composer, so it's easier to update.

We don't want yarn to update the lock file on install which
wouldn't be reproducible.

It's very CI specific