Power Display: Allow users to assign custom nicknames to monitors

### Description of the new feature / enhancement

Allow users to assign a custom nickname to each monitor in Power Display settings.

The nickname should be displayed in the flyout in place of or alongside the generic hardware name (e.g. `2475W`, `MSIMAG301RF`).

If per-monitor tray icons are implemented (see #48321), the nickname should also appear there as tool-tip.

### Scenario when this would be used?

Multi-monitor users often have semantically distinct displays ("Left", "TV", "Portrait", "4K").

Without nicknames, identifying which monitor is being controlled requires cross-referencing generic hardware names or going through Refresh > Identify monitors.

A user-defined nickname makes monitor identification immediate throughout the UI.

### Supporting information

- Related feature request: #48321
- ClickMonitorDDC supports custom monitor names

Start by reviewing the Power Display settings and flyout UI, then compare the related per-monitor tray icon request in #48321. Define where a user enters and edits each nickname, and verify that the nickname appears in the flyout alongside or instead of the hardware name and, if applicable, as a tray-icon tooltip.

Written by the indexing model from the issue text.