driconf: Use nesting macros for defining options.

driconf: Use nesting macros for defining options.

Manually balancing the BEGIN/ENDs is a recipe for xml validation failures,
just make the macros do the balancing.  The only ugly bit I think is that
enums take a list of DRI_CONF_ENUM() without ','s in between them.

Reviewed-by: Kristian H. Kristensen <hoegsberg@google.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6753>