[Tabs] Updates images of contained tabs to include panel

[aagonzales]

We need to add the content panel any contained tabs image to help users understand the relationship of the content panel to the tabs.

[laurenmrice]

Tracey is currently working on the website issues Tabs: Usage tab and Tabs: Style tab which will resolve this. She will be adding guidance around the tab panel and showing it in various images.

Design and A11y

• [x] It was mentioned there could be implications of adding the tab panel background to every contained tab image example on the website and it would be better to surface it in certain places where it would make the most sense.
• [x] Michael Gower has also made comments about wanting to include the tab panel in our website docs

Dev

• Just for further context in this related issue #14443: There was a dev concern if we should add this behind a feature flag in code. And if we know if everyone should always be using contained tabs with a panel background, or if there are particular instances where you don't need a tab panel background change? We can resolve that point in the #14443 issue.

[kingtraceyj]

tab panel images have been updated and tab panel with the correct layers are live.