MDL-68677 core: Correct usage of templaterev for caching templates
The M.cfg.templaterev variable should only be used to present persistent
caching, not caching of content within the same page load.
Preventing caching of same-page content makes it difficult to develop
for real user experiences as content is slow to load and does not give a
realistic and consistent loading experience.
This change affects the loading of partials specifically which notably
includes the loading spinner. Without this patch the loading icon is
often not seen at all because it does not load in a timely fashion and
the content being loaded is loaded first.
