bug: OpenImageIO is not able to write GPS tags to tiff files

[kjellpeterson-shotover]

Describe the bug
When writing an image file with ImageOutput, if the extra_attribs contains any GPS exif data (for example, GPS:Latitude) they will not be written to the file.

OpenImageIO version and dependencies
2.4.14 but the problem appears to exist in the latest version as well by code inspection

To Reproduce
easiest is to take a jpg with GPS tags and run oiiotool in.jpg -o out.tif

Evidence
example jpg file with GPS tags, example oiiotool output tif without GPS tags, example tif with GPS tags written by other means:

image_2026-02-16-140503.tif
out.tif

• Example input: If the problem only happens with certain image files, please
  attach the smallest image you can make that reproduces the problem.

IF YOU ALREADY HAVE A CODE FIX: There is no need to file a separate issue,
please just go straight to making a pull request.

[lgritz]

On it!

[lgritz]

Proposed fix (more extensive than I first thought) here: #5050

The GPS part was easy. The hard part was that some of the GPS attributes have data type patterns that are different than the standard or Exif TIFF tags (like Longitude needing an array of 3 rational numbers), and revealed a number of shortcomings that needed to be fixed to correctly handle those fields. But it was a great excuse to clean all of that up.