Auto merge of #98483 - dvtkrlbs:bootstrap-dist, r=jyn514

Distribute bootstrap in CI

This pre-compiles bootstrap from source and adds it to the existing `rust-dev` component. There are two main goals here:
1. Make it faster to build rust from source, both the first time and incrementally
2. Make it easier to add non-python entrypoints, since they can call out to bootstrap directly rather than having to figure out the right flags to pre-compile it. This second part is still in a bit of flux, see the tracking issue below for more information.

There are also several changes to make bootstrap able to run on a machine other than the one it was built (particularly around `config.src` and `config.out` detection). I (`@jyn514)` am slightly concerned these will regress unless tested - maybe we should add an automated test that runs bootstrap in a chroot or something? Unclear whether the effort is worth the test coverage.

Helps with rust-lang/rust#94829.

Author: bors