What?

Fixes #71951

In trunk, when clicking the Edit contents button on an unsynced pattern, the Block Inspector becomes empty.

Why?

The issue is that after clicking the 'Edit contents' button, neither of the tabs (Settings or Styles) is selected. From the 'before' screenshot you can see neither tab has the underline indicating selection.

The Tabs component still considers the 'Content' tab as the selected one, even though clicking 'Edit contents' removes it.

How?

Use the Tabs component as a controlled component. When the list of tabs changes, an effect checks that the selected tab is still present. If it's no longer present, the code falls back to the first tab being the selected tab.

Testing Instructions

1. Turn on the Gutenberg > Experiment: contentOnly: make patterns contentOnly by default upon insertion
2. Go to the site editor
3. Open the sidebar inspector
4. Select a pattern that defaults to contentOnly (or insert a new pattern, most should work)
5. Click the Edit contents button

In trunk: Sidebar contents disappear
In this PR: The Settings tab content is shown

Screenshots or screencast

Before	After