Use renovate to update more than just dependencies

[metalmatze]

Dependabot is enabled on this repository to take care of updating Go/Python dependencies. That's already great!

However, it can't update all sorts of other things that are worth keeping up-to-date in the repository like GitHub Actions, Dockerfiles, YAML Kubernetes manifests.

I propose switching to renovate which can also take care of all of these dependencies by configuring it to watch various resources, like Docker tags on a registry.

Here are some examples for our Parca demo-deployments repository which should be fairly similar:
parca-dev/demo-deployments#53
parca-dev/demo-deployments#54
parca-dev/demo-deployments#55