JTC Speed Scaling backport to Jazzy

[pastoriomarco]

Sorry to open a similar issue to one already closed (#2007), but I'd like to know if there's a practical reason why the speed scaling shouldn't be ported to Jazzy.
I tried to backport it in this fork with a very low-effort copy-paste approach (except turning get_lifecycle_id() to get_lifecycle_state().id() ) and for what I see it works. Jazzy also has all the needed msgs, while humble doesn't.

I didn't put too much effort on testing apart from the context where I need it, honestly.
If it's not something you'd rather avoid for some reason, I'll test a more in depth and open a PR, let me know!

[christophfroehlich]

The practical reason is limited available maintainer resources. As users can compile the rolling version on every active distro, we don't want to spend too much of our time in backporting new features.

[pastoriomarco]

Which is perfectly reasonable TBH.
I need the speed scaling in Jazzy in a workflow with docker containers: I can tweak the dockerfiles to build the rolling version, but since I'll be using this functionality massively and I'd like it to be simpler for other users to have it available, I tried this backport. At this point it's just a matter of simplifying the workflow rather than availability.

If you are ok with me opening a PR, I'll run more tests and go for it. If you'd just rather not backport, let me know!

[christophfroehlich]

I created #2105, if it needs changes: Could you please open a PR against it?