Group key management cluster XML looks nothing like the spec

[bzbarsky-apple]

Problem

The XML bits added in #12479 look nothing like the spec. The naming is off. The integer types used are wrong in a bunch of places (e.g. hardcoding sized ints for things like fabric indices, group ids, etc, some of them with the wrong sizes). Times are not using the epoch-us type, which is what the spec has. Nullable fields are not marked nullable. Attributes that are supposed to be marked writable are not marked writable.

Proposed Solution

Go through and make the XML match the spec.

[bzbarsky-apple]

Oh, and because it does not handle fabric index properly it's not getting the security checks around messing with other fabrics' data. So this is a critical security bug too.