Initial Exif and XML metadata support for JPEG XL

[ssh4net]

Description

Initial Exif and XML metadata support for JPEG XL. EXIF - works and enabled by default XML - works and enabled by default IPTC - that part need some help. JPEG XL support XML based IPTC, but I do not get what IPTC create an OIIO JBIG - not sure

new options: jpegxl:use_boxes - export EXIF, XMP, IPTC, JBIG jpegxl:compress_boxes - compress meta boxes (disabled for this moment by default)

jpegxl:exif_box = 1 (enabled) jpegxl:xmp_box = 1 (enabled) jpegxl:jumb_box = 0 (disabled) jpegxl:iptc_box = 0 (disabled)

Tests

Not yet, but if we have I can add.

Checklist:

• [x] I have read the contribution guidelines.
• [ ] I have updated the documentation, if applicable.
• [ ] I have ensured that the change is tested somewhere in the testsuite (adding new test cases if necessary).
• [ ] If I added or modified a C++ API call, I have also amended the corresponding Python bindings (and if altering ImageBufAlgo functions, also exposed the new functionality as oiiotool options).
• [x] My code follows the prevailing code style of this project. If I haven't already run clang-format before submitting, I definitely will look at the CI test that runs clang-format and fix anything that it highlights as being nonconforming.