Upgrade baseimage to Ubuntu 24.04

[MrSerth]

Description of the change

This PR upgrades the baseimage and dependent files for Ubuntu 24.04. As part of this upgrade, config files for syslog-ng were updated, too.

Here are some thoughts on the dedicated commits:

• I wasn't sure about the Vagrant file and Makefile. The Vagrant file seems to be a no-brainer, and a new noble64 box is already available. The Makefile should work again as soon as a new release was drafted.
• The syslog-ng.conf change was required due to the following warning and the newer version 4.3 shipping with Ubuntu 24.04:

  [2024-04-19T19:48:11.882330] WARNING: Configuration file format is too old, syslog-ng is running in compatibility mode. Please update it to use the syslog-ng 4.3 format at your time of convenience. To upgrade the configuration, please review the warnings about incompatible changes printed by syslog-ng, and once completed change the @version header at the top of the configuration file; config-version='3.35'
  [2024-04-19T19:48:11.882552] WARNING: Your configuration file uses an obsoleted keyword, please update your configuration; keyword='stats_freq', change='Use the stats() block. E.g. stats(freq(1));', location='/etc/syslog-ng/syslog-ng.conf:10:4'
  

  My changes resolve this warning.
• Adding the smart-multi-line.fsm is optional. I did so to resolve another warning:

  [2024-04-19T19:48:11.880283] smart-multi-line: error opening smart-multi-line.fsm file; filename='/usr/share/syslog-ng/smart-multi-line.fsm', error='No such file or directory (2)'
  [2024-04-19T19:48:11.880307] smart-multi-line: your smart-multi-line.fsm seems to be empty or non-existent, automatic multi-line log extraction will probably not work; filename='/usr/share/syslog-ng/smart-multi-line.fsm'
  

  Without adding the file, each start of syslog-ng (e.g., during the start of a container) would yield the above error message. As detailed in my commit message, the file added is taken unchanged from syslog-ng directly.
• The release badge on the README.md is broken, since the branch no longer exists. Hence, I decided to use the newest release workflow result, so that a suitable status is displayed at all times.

Benefits

A newer Ubuntu version is available and warnings normally issued with the upgrade are resolved.

Possible drawbacks

The new Ubuntu version and all the package version changes might include breaking changes. While I tried to test the changes and thereby discovered the syslog-ng changes, I cannot rule out that further changes are necessary.

Applicable issues

None

Additional information

Reviewing commit-by-commit is recommended.

[MrSerth]

Ubuntu 24.04 is expected to be released on Thursday, April 25th 2024. I've tested with the beta release, but would recommend to wait the remaining five days before merging. Hence, I've set this PR to draft.

Nevertheless, I would be happy to start reviewing already and to receive feedback. As soon as Ubuntu 24.04 is finally released, I will mark this PR as ready for review.

[MrSerth]

Ubuntu 24.04 has been released today. Hence, this PR is now ready.

[samip5]

I don't see anything particularly wrong.