Speedup the building of Docker images

[sandhose]

This is a split off #18033

This uses a few tricks to speed up the building of docker images:

• This switches to use uv pip install instead of pip install. This saves a bunch of time, especially when cross-compiling
• I then looked at what packages were not using binary wheels: I upgraded MarkupSafe to have binaries for py3.12, and got back to Python 3.12 because hiredis didn't have builds for py3.13 with the version we were using
• The generation of the requirements.txt is arch-agnostic, so I've switched this one to run on the build architecture, so that both arch can share it
• The download of runtime depdendencies can be done on the build architecture through manual apt-get download plus dpkg --extract
• We were using -slim images, but still installed a bunch of -dev dependencies. Turns out, all the dev dependencies were already installed in the non-slim image, which saves a bunch of time as well

[anoadragon453]

A few very minor things, but otherwise this LGTM. This included a few tricks I wasn't aware of myself. Thanks for taking the time to go through and do this!

Needs a git revert d113209 before merge, of course.

[anoadragon453]

LGTM after temp commit revert. Thanks!