Storybook: Add Story for BlockPopover

[dhruvikpatel18]

What?

This PR will add story for BlockPopover in the Storybook.

Why?

Part of: #67165
Part of: #22891

Testing Instructions

1. Run npm run storybook:dev
2. Open the storybook on localhost
3. Check the BlockPopover story.

Screenshots or screencast

BlockPopover.Screencast.mov

[github-actions]

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Co-authored-by: dhruvikpatel18 <dhruvik18@git.wordpress.org>
Co-authored-by: im3dabasia <im3dabasia1@git.wordpress.org>

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[im3dabasia]

Looks like CI is not happy. Could you fix that first? @dhruvikpatel18

[im3dabasia]

Thanks @dhruvikpatel18 !

Good work to start with. Left a few feedbacks.

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Two things worth calling out as good — the __unstablePopoverSlot / __unstableContentRef props are correctly left out, since the public wrapper strips them.

The extra BlockList and provider are fine here, they're the minimum needed for BlockPopover to have a block element to anchor to, without which it returns null (index.js:106-108).

[im3dabasia]

LGTM