Septentrio v1.15 backport cleanup

[mrpollo]

The previous PR #23386 broke the release branch due to unintentional file overwrites. Hopefully, this PR captures the intention and the functionality.

We need Septentrio to verify this PR builds, flashes, and works before merging.

cc @chiara-septentrio, @flyingthingsintothings

[hamishwillee]

Note, does this imply a need for docs backport @flyingthingsintothings ?

[flyingthingsintothings]

Yes, the documentation for v1.15 would have to be updated with the same changes that were made to the main documentation.

[chiara-septentrio]

It's probably my fault, it built correctly but the difference in files might not have been updated when making the pull request and I didn't think to check more than the difference I saw on the web interface. So sorry for that.

[julianoes]

I've added the commits from #23415 as well.

[bresch]

v1.15 having conflicting serial configs due to septentrio params: https://github.com/PX4/PX4-Autopilot/issues/23714#issuecomment-2370671684

[mrpollo]

Thanks for the report @bresch I will take a look

[mrpollo]

This pr was cherry-picked by @dagar no longer needed so I am closing