Merge appxsigner into windowsbinariessigner
This MR
- merges the application IDs from appxsigner's project settings to windowsbinariessigner's project settings,
- removes the separate "sign APPX" step from the Craft Windows jobs,
- and remove settings and documentation of appxsigner.
I have tested the changes with NeoChat 23.08: https://invent.kde.org/network/neochat/-/jobs/1552007