qapi: Plug trivial documentation holes around former simple unions

The conversion of simple to flat unions left the @data members
undocumented.  Add documentation where it's trivial.  Copy verbatim
from the wrapped type's description where possible.

Leftovers: String (to be taken care of in the next commit), and
TransActionAction (left for another day).

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-ID: <20240205074709.3613229-13-armbru@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
diff --git a/qapi/block-core.json b/qapi/block-core.json
index 80ed412..55b583f 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -196,6 +196,8 @@
 ##
 # @ImageInfoSpecificQCow2Wrapper:
 #
+# @data: image information specific to QCOW2
+#
 # Since: 1.7
 ##
 { 'struct': 'ImageInfoSpecificQCow2Wrapper',
@@ -204,6 +206,8 @@
 ##
 # @ImageInfoSpecificVmdkWrapper:
 #
+# @data: image information specific to VMDK
+#
 # Since: 6.1
 ##
 { 'struct': 'ImageInfoSpecificVmdkWrapper',
@@ -212,6 +216,8 @@
 ##
 # @ImageInfoSpecificLUKSWrapper:
 #
+# @data: image information specific to LUKS
+#
 # Since: 2.7
 ##
 { 'struct': 'ImageInfoSpecificLUKSWrapper',
@@ -223,6 +229,8 @@
 ##
 # @ImageInfoSpecificRbdWrapper:
 #
+# @data: image information specific to RBD
+#
 # Since: 6.1
 ##
 { 'struct': 'ImageInfoSpecificRbdWrapper',
@@ -231,6 +239,8 @@
 ##
 # @ImageInfoSpecificFileWrapper:
 #
+# @data: image information specific to files
+#
 # Since: 8.0
 ##
 { 'struct': 'ImageInfoSpecificFileWrapper',