API layer version is inconsistently specified

[fredemmott]

• per https://registry.khronos.org/OpenXR/specs/1.0/man/html/XrApiLayerProperties.html "It is an integer [uint32_t], increasing with backward compatible changes."
• per https://registry.khronos.org/OpenXR/specs/1.0/loader.html, "implementation_version" is a string field in the JSON, and "If the API layer itself has any major changes, this number should change."

Concrete issues:

• The JSON is not documented a requiring a uint32_t or even an integer, but it should presumably match
• I'm assuming that "backwards compatible" is a typo, and "backwards incompatible" is meant ?
  either way, it has a different meaning to "any major changes"
• There'd also be some debugging value to being able to represent the actual human-readable version number, rather than just a "major changes" version. In practice, I think most layers just use "1".
  This would require either that an arbitrary string is allowed, or a much larger type than uint32_t (especially for layers that increment the version number in every CI build). Currently, the description field could be (ab?)used for this

[rpavlik-bot]

An issue (number 2321) has been filed to correspond to this issue in the internal Khronos GitLab (Khronos members only: KHR:openxr/openxr#2321 ), to facilitate working group processes.

This GitHub issue will continue to be the main site of discussion.