backport decoding improvements for libjxl

[goodusername123]

Brings over various decoding improvements from the libjxl repo (including one change that hasn't been officially added yet). changes ranging from quality to speed to stability.

If you prefer a better option compared to this PR might just be updating the copy of libjxl to the latest main branch from the official libjxl repo (which would include all the changes in this PR minus one) and then manually merging in the single pull request that hasn't been merged into the libjxl repo (this being the unmerged PR: libjxl/libjxl#4516)

examples.zip (JXL files that show noticeable visual improvements with these changes)

here is an example of the blue noise dithering (officially merged in main libjxl repo) and the decoding colorspace being changed to sRGB (not officially merged in main libjxl repo). These animated visual examples are being used here with permission from the creator:

below are all the changes brought in (only the bottom one isn't actually apart of the main libjxl repo)
libjxl/libjxl@2a4f12b
libjxl/libjxl@69ae5fb
libjxl/libjxl@a75b322
libjxl/libjxl@67a6f18
libjxl/libjxl@44eb4f9
libjxl/libjxl@e396172
libjxl/libjxl@c5a2fb5
libjxl/libjxl@4717d7d
libjxl/libjxl@e1fff8b
libjxl/libjxl@81247d5 (partial)
libjxl/libjxl@b3ebbf0
libjxl/libjxl#4516

[MrAlex94]

Thanks - have gone through and looks good.

Speaking of, looks like jxl-rs support is tentatively ready to be merged: https://bugzilla.mozilla.org/show_bug.cgi?id=1986393 & https://bugzilla.mozilla.org/show_bug.cgi?id=1987386

If I've got time, might pull that in to replace libjxl.

[jonnyawsom3]

jxl-rs is still single-threaded currently, so it may be worth waiting to avoid a performance regression.