Adapt all demos to Beluga 2.0

[hidmic]

Proposed changes

Closes #6. Depends on https://github.com/Ekumen-OS/beluga/pull/419. This somewhat large patch restores compatibility between Beluga demos (our official demos now, no longer supplementary material for some submission) and latest Beluga.

Type of change

• [x] 🐛 Bugfix (change which fixes an issue)
• [x] 🚀 Feature (change which adds functionality)
• [x] 📚 Documentation (change which fixes or extends documentation)

Checklist

• [x] Lint and unit tests (if any) pass locally with my changes
• [x] I have added tests that prove my fix is effective or that my feature works
• [x] I have added necessary documentation (if appropriate)
• [x] All commits have been signed for DCO

Additional considerations

This patch not only updates custom particle filter implementations to use the most recent APIs but also reorganizes the repository to be in harmony with the recently added beluga_nav2 integration demo and to lay the ground for more additions to come.

[hidmic]

Whoops. This is not merged. I'll merge by EOD. FYI @glpuga @Alondruck.