qapi: convert "Example" sections with titles

When an Example section has a brief explanation, convert it to a
qmp-example:: section using the :title: option.

Rule of thumb: If the title can fit on a single line and requires no rST
markup, it's a good candidate for using the :title: option of
qmp-example.

In this patch, trailing punctuation is removed from the title section
for consistent headline aesthetics. In just one case, specifics of the
example are removed to make the title read better.

See commit-4: "docs/qapidoc: create qmp-example directive", for a
              detailed explanation of this custom directive syntax.

See commit+2: "qapi: remove "Example" doc section" for a detailed
              explanation of why.

Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Message-ID: <20240717021312.606116-8-jsnow@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>

qapi/ui.json

@@ -1270,9 +1270,8 @@
 #    property, so it is possible to map which console belongs to which
 #    device and display.
 #
-# Examples:
-#
-#     1. Press left mouse button.
+# .. qmp-example::
+#    :title: Press left mouse button
 #
 #     -> { "execute": "input-send-event",
 #         "arguments": { "device": "video0",
@@ -1286,7 +1285,8 @@
 #                        "data" : { "down": false, "button": "left" } } ] } }
 #     <- { "return": {} }
 #
-#     2. Press ctrl-alt-del.
+# .. qmp-example::
+#    :title: Press ctrl-alt-del
 #
 #     -> { "execute": "input-send-event",
 #          "arguments": { "events": [
@@ -1298,7 +1298,8 @@
 #               "key": {"type": "qcode", "data": "delete" } } } ] } }
 #     <- { "return": {} }
 #
-#     3. Move mouse pointer to absolute coordinates (20000, 400).
+# .. qmp-example::
+#    :title: Move mouse pointer to absolute coordinates
 #
 #     -> { "execute": "input-send-event" ,
 #       "arguments": { "events": [