Refactor ph label cleanup functions

[markheckmann]

We might consider slightly refactoring https://github.com/Majid-Eismann/robocop/blob/main/R/layout.R

• The functions layout_duplicate_rename and layout_duplicate_delete are almost identical, hence we have quite some code duplication here.
• Also it would be helpful to inform the user what is actually happening, i.e. which placeholder labels are (will be) renamed / deleted. Maybe adding a dryrun option would also make sense.

[markheckmann]

A function to clean placeholder labels should probably be part of the officer package, as you already suggested in this issue. As long as its not integrated in officer, it should probably be a separate exported function here, with a naming matching the officer convention. Maybe layout_check_ph or layout_dedupe_ph or similar would be suitable? The function can then either rename, delete or just inform the user about duplicated ph labels, for example like this:

layout_dedupe_ph(x, action = c("check", "rename", "delete"))