Switch stable-rc reports to the new infra

@crazoes has been compiling stable-rc reports using using the legacy system and dashboard. That is a quite painful process with a lot of manual steps. It's time to move that reporting to the new era, even if that means reducing the coverage of build and boot temporarily.

**Current coverage**. According to [latest dashboard report](https://linux.kernelci.org/test/job/stable-rc/branch/linux-6.8.y/kernel/v6.8.9/plan/baseline/) we have boot tests running in 4 labs:

* lab-broonie
* lab-collabora
* lab-kontron
* lab-pengutronix

With @nuclearcat making the first real production deployment of the new infra, it is now feasible for labs to start connecting themselves to the new lab. This task is to track that from a pov of stable-rc reports.

Beyond that, we would also need to:

- [ ] enable a few more builds compare to the current support in legacy (@nuclearcat)
- [ ] have the results-summary tool show all the need information (Helen)