Improve status message when settling is taking too long

### Enhancement Proposal

When deploying COS Proxy at scale, it takes quite a while for the units to settle if the proxy is related to COS prior to being related to the workloads.

This is easily resolved by changing the order of relating to wait for the proxy to settle prior to relating it to COS.

Currently, the status message is empty while the proxy is processing. This should be improved by setting a status message whenever it takes too long (>5m?) for it to settle.

It should also say that its prcessing proxied relations when that is the case

The issue names no files or tests; start by locating the status-message handling and the proxied-relation processing entry points. Reproduce the deployment order where the proxy relates to COS before workloads, then verify that a long-running settlement reports processing and proxied relations instead of leaving the status empty.

Written by the indexing model from the issue text.