Stop polling CPU specs when popouts like dankdash, processlist aren't visible

### Feature Description

The CPU specs poll causes consistent CPU spike in a regular interval for the `qs` process. This won't happen unless the dash or the processlist popout hasn't been opened once on fresh boot.

### Use Case

Cuts resource usage. Stop qs process from jumping up and down in `top`/`btop`.

### Compositor(s)

All compositors

### If Other, please specify

_No response_

### Proposed Solution

This will likely touch many qs components and would best also be downstreamed to plugins/desktop widgets as well.

### Alternatives/Existing Solutions

_No response_

No files or tests are named. Start by tracing the CPU specs polling and how visibility is tracked for the dankdash and processlist popouts. Done means polling stops while those popouts are hidden, resumes when needed, and the reported CPU spikes are reduced without breaking visible usage.

Written by the indexing model from the issue text.