binding: introduce XGL_DESCRIPTOR_SET_LAYOUT_CHAIN

Replace a chain of XGL_DESCRIPTOR_SET_LAYOUT by
XGL_DESCRIPTOR_SET_LAYOUT_CHAIN.  The change also drops
stageFlags/pSetBindPoints, and affects xglUpdateDescriptors().

xglCmdBindDescriptorSet() is not updated yet by this commit, which makes it
impossible to bind multiple sets.

The change also encourages the use of arrays of resources, which we do not
support.

v2: fix a typo in intel_desc_set_update_samplers() that prevents it from
working (olv)
diff --git a/include/xglDbg.h b/include/xglDbg.h
index 7e655e6..41b4b3b 100644
--- a/include/xglDbg.h
+++ b/include/xglDbg.h
@@ -91,6 +91,7 @@
     XGL_DBG_OBJECT_BUFFER,
     XGL_DBG_OBJECT_BUFFER_VIEW,
     XGL_DBG_OBJECT_DESCRIPTOR_SET_LAYOUT,
+    XGL_DBG_OBJECT_DESCRIPTOR_SET_LAYOUT_CHAIN,
     XGL_DBG_OBJECT_DESCRIPTOR_POOL,
 
     XGL_DBG_OBJECT_TYPE_BEGIN_RANGE = XGL_DBG_OBJECT_UNKNOWN,