Support scraping config-reloader sidecar for Thanos Ruler

[philipgough]

• [x] I added CHANGELOG entry for this change.
• [] Change is not relevant to the end user.

Changes

Adds config to allow scraping of the Thanos Ruler config reloader sidecar.

Verification

Deployed on minikube, look at the targets page and see thanos ruler with the desired endpoint is up.