Fix: use active variation as the parent block if available

[dinhtungdu]

What?

This PR shows the active variation info in the inner block's menu if the parent block is a variation.

Why?

Fixes #44608

If the current parent block is a variation, it's better to display the variation title and icon in the block menu. Otherwise, it can make users confused.

How?

This PR checks if the first parent block is a variation and then uses the active variation as the parent block, so the correct metadata is displayed in the block menu: Select parent block (...) item.

Testing Instructions

1. Add a Row block to the page.
2. Add a Heading block to the Row block.
3. Open the menu of the Heading block.
4. See Select parent block (Row).

Or check out this PR, add a filter block to the page and check the block menu of inner block as screenshots show: woocommerce/woocommerce-blocks#6978

Screenshots or screencast

Before this PR

With this PR

[carolinan]

I tested this by adding a row group block variation with a paragraph inside.
Before: The menu would show "Select parent block (group)"
With PR: The menu shows "Select parent block (row)"
The pr works well in my test.

[dinhtungdu]

I tested this by adding a row group block variation with a paragraph inside.

Using Row is much easier for testing. I updated the reproduce steps using yours, thank you so much!

[ntsekouras]

Looks good, thanks @dinhtungdu !