thumbnail: Support jxl and plumbing for future formats.

[Quackdoc]

This will allow using jxl-oxide for thumbnail creation, it seems to be working well for me but it's a draft for a couple reasons, the primary one is im not sure the best resource limit to set. I feel like this should be set in a configuration, but even then I don't know what defaults should be used.

the current value I found to be necessary for some of my images, but likely way to high for lower end systems. (that being said, hitting an oom case in cosmic-files is much better then having a thumbnailer oom since oomd will actually kill cosmic-files instead of the entire compositor)

[jackpot51]

I would recommend a much lower memory limit and potentially a lower number of jobs.

[Quackdoc]

added configuration (just the file config) and changed the default to 4 parallel with with a max of 2000mb usage, which is inline with image-rs 512mib default limit. Also added adjustment for max file size to check for. image-rs also has a configurable limit too now.

I figure the defaults should be good enough for low end systems.

[Quackdoc]

I think this is more or less ready to review with a small cleanups I haven't pushed. should jxl-oxide try to convert the thumbnail to sRGB? It will help thumbnails look better, but may give false impression when an image is for instance an HDR image.

[jackpot51]

Yes, the thumbnails should be sRGB.

[Quackdoc]

ah, so jxl-oxide's image-rs doesn't currently handle the colorspace conversions, I can probably add it to jxl-oxide but that would probably put off the PR for a bit.

Image-rs doesn't handle colorspace conversions anyways so the current configuration is inline with what it was doing before, I think using an external cms instead of exposing jxl-oxide's cms is probably better for consistency and can be done in a separate PR.