Reusing system overview stats

### Feature Description

I have the system monitor desktop widget activated and it monitors the . However, when I open the System overview (`dms ipc processlist open`) the history in the performance tab is completely empty.
So I asked myself if the stats history (which is always recorded by the system monitor desktop widget) could be reused so it already shows some history when one opens the system monitor window.

### Use Case

It would give a faster overview of the system.

### Compositor(s)

- [x] All compositors
- [ ] Niri
- [ ] Hyprland
- [ ] MangoWC (dwl)
- [ ] Sway
- [ ] Other (specify below)

### Proposed Solution

_No response_

### Alternatives/Existing Solutions

_No response_

Start by running `dms ipc processlist open` and inspect the System overview performance tab alongside the active system monitor desktop widget. Trace where each view obtains and stores its stats history; done means the performance tab shows the widget's existing history when the overview opens, without requiring new samples.

Written by the indexing model from the issue text.