docs: link pyroscope docs to COS docs or charmhub.io docs

### Enhancement Proposal

ATM the pyroscope docs are unreachable from either [charmhub.io](https://charmhub.io/pyroscope-coordinator-k8s) or the[ o11y docs](https://documentation.ubuntu.com/observability/latest/).

We should probably ensure that the COS documentation links to pyroscope (under the 'peripheral charms' section for example). Or if we decide that pyroscope is just not related to COS, we should create a separate root for it like we did for chaos engineering.

Start by opening the linked charmhub.io and observability documentation pages, then inspect how the existing chaos engineering documentation is organized. Decide whether Pyroscope belongs under the COS “peripheral charms” section or needs a separate root. Done means the Pyroscope documentation is reachable from the chosen location and the links render correctly.

Written by the indexing model from the issue text.