Block Bindings: Refactor the way sources are handled

[gziolo]

Trac ticket: https://core.trac.wordpress.org/ticket/60282

Follow-up for #5888.

It fixes the coding style issues reported. It goes further and improves the code quality it other places where the logic for block bindings was added.

There are no functional changes.

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[github-actions]

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Props: gziolo, mukesh27, youknowriad, santosguillamot.

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[youknowriad]

Thanks for handing the follow-up @gziolo I appreciate it. On a quick glance, everything looks good to me.

[youknowriad]

This kind of private function is in general better as inline functions/closures. I think these are not authorized in Core yet right? Do you know more about the reasoning...

[gziolo]

I was thinking about it, too. I’ll ask around and check the codebase. The only benefit of using another regular function like at the moment is the PHPDoc included.

[gziolo]

You definitely can find places where inline functions are defined as params passed. You shouldn't use them when passing the callback to WP hooks, but here, it would make perfect sense. I'll confirm that and refactor the code, if possible, after adding more unit tests.

[SantosGuillamot]

It looks good to me and the refactor makes sense 🙂

[gziolo]

Committed with https://core.trac.wordpress.org/changeset/57526.