ci: Add uncrustify style checks
This MR allows merge requests to be linted for style inconsistencies using Uncrustify.
Almost every line of code in this MR is inspired by phoc!495 (merged).
We reuse the uncrustify.cfg
used in Phoc. May be in future, it can be moved to a common repository so all apps in Phosh ecosystem can have single unified Uncrustify configuration.