Trusted Publishing: start by migrating pip-tools

[webknjaz]

There's a release request that nobody really can handle, as there's no lead that is active right now: jazzband/pip-tools#2112.
I've been fixing up the CI to get it to a green state lately, and I remembered talking to @jezdez regarding migrating to Trusted Publishing to eliminate the need to proxy the releases through Jazzband's private index.

I've made a PR with a PoC that roughly keeps the process the same, short of using a private index: jazzband/pip-tools#2149. But in order to go ahead, we should figure out all the configuration bits that aren't available to me.

@jezdez could you take a look and see what's needed to move this forward and perhaps learn how to scale it to other projects.

P.S. This is not asking to make me lead. Let's hope somebody shows up for the release and focus on things that are actionable.