XML Representation for Vendor Extensions Promoted to KHR Extensions

There are a couple of places in the XML file where an enum block has been allocated for a vendor, then the vendor extension has been promoted to a KHR extension that reused the vendor extension enum values. For example:

```xml




....
```

Some of the spec scripting was looking for KHR enums by parsing the `vendor` and was hence skipping these blocks. Should we handle this case by:

* Fixing the XML file? For example, we could either reassign this block to Khronos, or introduce a tag that scripts could look for that indicates the block also contains KHR enums.
* Fixing the scripts? Is there another way the scripts should identify KHR enums?

Start by locating the XML enum blocks for promoted vendor extensions and the spec scripts that identify KHR enums from the vendor attribute. Compare how these blocks are currently parsed and determine whether the XML or scripts should define their KHR status. Done means promoted KHR enums are consistently included by the specification tooling.

Written by the indexing model from the issue text.