feat: enforce shutdown sequencing of components

[drahnr]

We start to have more and more IO backed datastructures that are kept "alive" by free tasks. Depending on shutdown ordering, artifacts like pthread invalid arg and friends show up in CI, and during restart of components in production. We want to avoid this as much as possible and enforce ordering of shutdown tasks.

Commonly this is done via CancellationTokens (see https://tokio.rs/tokio/topics/shutdown )

[Mirko-von-Leipzig]

Something to also consider is using a more structured runtime aka not tokio. The benefit of tokio is that we don't have to think very hard about how to allocate resources e.g. thread pools, and they all share. However this is also a downside, as well as the lack of structure concurrency.

This is probably not worth the effort though given the wide tokio ecosystem support.