Use one-time bindings in the annotation component's template
for expressions whose values cannot change during the lifetime
of an annotation card.

Testing using the default /stream view, without scrolling:

Initial status as of 1ceb5fcefd7fa057bdbcf1f73df57d007289531f averaged
over 30+ digest cycles:

 Digest cycle: ~30ms
 Watchers: 1686

With this commit:

 Digest cycle: ~26ms
 Watchers: 1649