libjxl: update to 0.12

[yoshiyoshyosh]

Testing the changes

• I tested the changes in this PR: YES
  • I've been running my own master branch libjxl and periodically updating it in the past several months. I haven't thoroughly tested every dependency, but they do all build. most of the changes are fixes and optimizations.

Local build testing

• I built this PR locally for my native architecture, x86_64-glibc