dms_conversion_catalog: use proper activity queue

Because this is using SQLDict, when we had multiple conversion
activities for the same path with different conversion parameters, only
one was executed.

We don't want this here, as the recent failures on
testDmsWithPreConversion.TestDocumentWithPreConversion are showing, when
the same image is referenced with different conversion parameters we
want to pre-convert for all conversion parameters.

Use SQLQueue, which allows calling the same method more than once.

/reviewed-on nexedi/erp5!971

bt5/erp5_dms_conversion_catalog/SkinTemplateItem/portal_skins/erp5_dms_conversion_catalog/WebPage_preConvertReferencedImageList.py

@@ -63,4 +63,4 @@ for image_url in image_url_list:
           if format not in MARKER and quality not in MARKER:
             # format is mandatory if it's missing then anyway URL request will fail so
             # don't bother create an activity
-            document.activate(priority=4, tag="conversion").Base_callPreConvert(**convert_kw)
+            document.activate(priority=4, tag="conversion", activity="SQLQueue").Base_callPreConvert(**convert_kw)