Consider switching to gexiv2's new *_try_* style functions that pass on error details

gexiv2 0.12.2 from 2021-02-20 introduced a new set of functions that can return a proper detailed error structure instead of just logging the error to the console and returning `false`. These are named with a "`_try_`" component, e.g. `gexiv2_metadata_try_get_exif_tag_rational` instead of `gexiv2_metadata_get_exif_tag_rational`.

We are not currently using these, but perhaps we should be?

This would require breaking many APIs. It would also require the local gexiv2 library version to be >= 0.12.2, which would rule out Debian Bullseye and distros derived from it. However, Bookworm is just entering its freeze now (early 2023), so when that releases it may be OK.