feat: Add support for setting icon & template at same time (#14357)

* [macos] Add support for setting icon & template at same time

Calling set_icon and then set_icon_as_template in sequence
cause a flicker as they both run on the main thread and update
the UI. This exposes a single function to do both at once,
preventing the flicker.

* Format

* Update changed.md

---------

Co-authored-by: Fabian-Lars <30730186+FabianLars@users.noreply.github.com>