As reported by Liam, apparently for someone with a lot of filters, these
node creations just to check the aux input may add up noticeable time on
boot (it may also depend on the OS too? I didn't have any noticeable
delay personally).
Unfortunately we cannot know the presence of an aux input just with
class introspection because they can be registered by the op at runtime.
This optimization is therefore twofold:
* Since we know which filters have an aux input among all the ones with
hardcoded actions, we also hardcode this data. It means we only do the
actual check on non-hardcoded operations (third-party filters but also
GEGL operations which are not specifically listed in our code).
* I only do these checks once, stored by name in a hash table, because
filters_actions_setup() is actually run several times (for different
menus).
This should improve startup time a lot for people who experienced this
delay.
05e90b1cde