Add color metadata from libraw

[demoulinv]

Description

Add pre_mul, cam_mul, rgb_cam and cam_xyz arrays availbale in Libraw color info in OpenImageIO metadata. These metadata are prefixed with "raw:". 2D arrays rgb_cam and cam_xyz are delivered as 1D arrays. These metadata are fully documented in Libraw: https://www.libraw.org/docs/API-datastruct.html#libraw_colordata_t. This PR is related to issue https://github.com/OpenImageIO/oiio/issues/3538.

Tests

Checklist:

• [X] I have read the contribution guidelines.
• [ ] If this is more extensive than a small change to existing code, I have previously submitted a Contributor License Agreement (individual, and if there is any way my employers might think my programming belongs to them, then also corporate).
• [ ] 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).
• [X] My code follows the prevailing code style of this project.