Fix: Post Template block: 'List view' display setting should be selected by default

[hbhalodia]

Fixes #61569

What?

• Issue - Post Template block: 'List view' display setting should be selected by default #61569

Why?

• This PR adds the List View as default for the post template block.

How?

• On checking, we identified that, Layout is coming as an attribute inside the post template block. We checked if that is undefined, set it as the default list view.

Testing Instructions

• Open, any page.
• Add the query loop block and select any pattern.
• You would see now the list view is by default selected for that pattern.

Testing Instructions for Keyboard

• NIL

Screenshots or screencast

- You can see that, list type is selected by default.

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Co-authored-by: hbhalodia <hbhalodia@git.wordpress.org>
Co-authored-by: afercia <afercia@git.wordpress.org>

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[afercia]

Thanks for this PR @hbhalodia. Not my area of expertise but I'd investigate why the Post Template block doesn't have the layout attribute default in the block.json in the first place.
Cc @tellthemachines I see relevant changes from #49050 your eyes here would be appreciated 🙏🏽