Reorder executor docs a bit, add first stub of bare-metal docs

Created by: mrnugget

This started out with me fixing a bunch of typos and ended up with me reordering things and adding a first version of the bare-metal docs so we know where they would be.

(I still need to dogfood the bare-metal deployment here, including the dependency installation, so I'll probably change details.)

See screenshots below, since they're easier to digest in a PR than the diff.

My main goal was to make explicit which steps are required and when and to show visually which options are available. Hence a lot of lists and bullet points.

I also added a lot of cross-links so that new readers always end up where they need to be and/or can get additional context from other pages.

Screenshots

Deploy Executors 1

Deploy Executors 2