qapi: expose all schema features to code

This replaces use of the constants from the QapiSpecialFeatures
enum, with constants from the auto-generate QapiFeatures enum
in qapi-features.h

The 'deprecated' and 'unstable' features still have a little bit of
special handling, being force defined to be the 1st + 2nd features
in the enum, regardless of whether they're used in the schema. This
retains compatibility with common code that references the features
via the QapiSpecialFeatures constants.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Message-ID: <20250205123550.2754387-5-berrange@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
[Imports tidied up with isort]
Signed-off-by: Markus Armbruster <armbru@redhat.com>

scripts/qapi/visit.py

@@ -356,8 +356,9 @@ class QAPISchemaGenVisitVisitor(QAPISchemaModularCVisitor):
 #include "qemu/osdep.h"
 #include "qapi/error.h"
 #include "%(visit)s.h"
+#include "%(prefix)sqapi-features.h"
 ''',
-                                      visit=visit))
+                                      visit=visit, prefix=self._prefix))
         self._genh.preamble_add(mcgen('''
 #include "qapi/qapi-builtin-visit.h"
 #include "%(types)s.h"