Exercise more OpenImageIO build dependencies

OpenImageIO should be able to find all of its optional build-time dependencies in the CI container image:

- ffmpeg
- libheif
- hdf5
- libraw

Also it currently doesn't find J2K/openjpeg even though it is included (could be an incomplete CMake configuration).

Start by inspecting the CI container image dependency definitions and OpenImageIO's CMake configuration. Verify how ffmpeg, libheif, hdf5, libraw, and openjpeg are installed and detected; done means the CI image exposes all five optional dependencies and OpenImageIO finds them during configuration.

Written by the indexing model from the issue text.