Note [Ticks on applications]

Ticks such as source location annotations can sometimes make their way
onto applications (see e.g. #21697). So if we see something like

    App (Tick _ f) e

we need to descend below the tick to find what the real function being
applied is.

The resulting RULE also has to be able to match this annotated use
site, so we only look through ticks that RULE matching looks through
(see Note [Tick annotations in RULE matching] in GHC.Core.Rules).