Fix drag and drop panels in rows

[mdvictor]

This fixes panel positioning glitching when drag/dropping a panel into a row.

There were 2 issues:

• Moving panels into/out of rows caused a existing parent warning
• After moving a panel into a row, when calling toggleRow the firstPanelYPos here would be wrongly selected because sortChildrenByPosition would not sort row children also, thus causing a glitch.

Fixes https://github.com/grafana/grafana/issues/83292

📦 Published PR as canary version: 4.1.1--canary.663.8521906375.0

:sparkles: Test out this PR locally via: ```bash npm install @grafana/scenes@4.1.1--canary.663.8521906375.0 # or yarn add @grafana/scenes@4.1.1--canary.663.8521906375.0 ```

[grafanabot]

:rocket: PR was released in v4.1.1 :rocket: