Fixes to publishing of DEB packages to APT repo

[joaopalet]

• Give GPG key fingerprint instead of key ID to Aptly for the signing of the release
  • Even though Aptly specifies in the docs that gpg-key expects a key ID, it actually expects a key fingerprint
• Disable the key database daemon (keyboxd):
  • Since version 2.3.0 of gnupg all imported keys are stored in a SQLite database instead of using the specified keyring, and we need to import the key to a custom keyring to use them with Aptly
• Rename Linux package name to stackit
• Make APT distribution name consistent across all steps of the script
• Removes rootDir from custom Aptly config file (as defaults to the default value)
• Improve comment and job name of workflow