Shows either "Search by Name" or "Search by Key-Binding" as placeholder text in
the search button. This makes it more clear what's expected to be entered here.
Personally I often did/do the mistake of searching for the wrong thing in this
button, because I forgot that I changed it earlier. The placeholder text can
avoid this mistake.
Pull Request: https://projects.blender.org/blender/blender/pulls/113681