Removing separate OpenCL Extensions from the repository

Once we integrate all the khr extensions into the API and C specs, the
separate documents under ext/ will serve no purpose and will have the
risk of creating divergences between the sme content in the API / C
specs and the separate extension spec.

This removes the separate khr extension documents from the repo, and
strips down the OpenCL Extension spec to just point to the corresponding
extension appendix in the API spec. It will also serve as a forcing
function for all future extension development to be done against the API
/ C specs. Any outstanding PRs against these documents will have to be
rebased and the same edits reapplied to those specs, whether changes to
published extensions or in-flight, but as yet unpublished khr
extensions.

Ideally this would merge into #950 before that is merged to main, if the
WG can agree to that. It could also be retargeted to main instead, if
this decision will take longer than the timeframe for merging #950.
53 files changed