add a script to find and apply package updates

[jjhelmus]

Add scripts/update_downloads.py, which finds updates to the entries in pythonbuild/downloads.py. The optional --write argument write any updates, including calculated metadata to the file.

Run using:

uv run scripts/update_downloads.py

[jjhelmus]

This script was largely AI generated using Codex. The prompt that began the session was:

Write a Python script that can find possible updated versions of the packages in pythonbuild/downloads.py. The script should have options to list update new versions and then optionally make the necessary changes to pythonbuild/downloads.py. Have the process that checks for new versions be flexible as the projects have different constraints on versions and some are sourced from mirrors and the upstream URL must be checked rather than the mirror.

I have used this script to kick off many of the recent update including #1153, #1156, and #1157.

I plan on testing it with the upcoming 3.15.0b3 release.

[jjhelmus]

Should have tagged this with ci:skip but CI is already running.

This work could be expanded to include tests and an actions to run + apply changes on a regular schedule. That can be done later if needed.

[jjhelmus]

Example results:

❯ uv run scripts/update_downloads.py 
autoconf: 2.72 -> 2.73 (mirrored)
  https://ftp.gnu.org/gnu/autoconf/autoconf-2.73.tar.gz
binutils: 2.43 -> 2.46.1 (mirrored)
  https://ftp.gnu.org/gnu/binutils/binutils-2.46.1.tar.xz
bzip2: 1.0.8 (current)
cpython-3.10: 3.10.20 (current)
cpython-3.11: 3.11.15 (current)
cpython-3.12: 3.12.13 (current)
cpython-3.13: 3.13.14 (current)
cpython-3.14: 3.14.6 (current)
cpython-3.15: 3.15.0b2 (current)
expat: 2.8.1 (current)
libedit: 20240808-3.1 -> 20260512-3.1
  https://thrysoee.dk/editline/libedit-20260512-3.1.tar.gz
libffi: 3.4.6 -> 3.4.8
  https://github.com/libffi/libffi/releases/download/v3.4.8/libffi-3.4.8.tar.gz
libpthread-stubs: 0.5 (current)
libX11: 1.8.13 (current)
libXau: 1.0.12 (current)
libxcb: 1.17.0 (current)
m4: 1.4.19 -> 1.4.21 (mirrored)
  https://ftp.gnu.org/gnu/m4/m4-1.4.21.tar.xz
mpdecimal: 4.0.0 -> 4.0.1 (mirrored)
  https://www.bytereef.org/software/mpdecimal/releases/mpdecimal-4.0.1.tar.gz
nasm-windows-bin: 2.16.03 -> 3.01 (mirrored)
  https://www.nasm.us/pub/nasm/releasebuilds/3.01/win64/nasm-3.01-win64.zip
ncurses: 6.5 -> 6.6 (mirrored)
  https://ftp.gnu.org/gnu/ncurses/ncurses-6.6.tar.gz
openssl-3.5: 3.5.7 (current)
patchelf: 0.13.1 -> 0.18.0
  https://github.com/NixOS/patchelf/releases/download/0.18.0/patchelf-0.18.0.tar.bz2
pip: 26.1.2 (current)
setuptools: 82.0.1 (current)
tcl: 9.0.3 (current)
tk: 9.0.3 (current)
x11-util-macros: 1.20.2 (current)
xcb-proto: 1.17.0 (current)
xorgproto: 2025.1 (current)
xtrans: 1.6.0 (current)
xz: 5.8.3 (current)
zlib: 1.3.2 (current)