Custom Posts: Show published pages with hierarchy

[crazytonyli]

Description

In the existing Pages screen, all pages are fetched and reorganized into a tree. This PR implements the same on the custom post list.

Testing instructions

Compare the existing Pages screen with the one backed by the wordpress-rs library. They should show the same list of pages.

[dangermattic]

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📲 You can test the changes from this Pull Request in WordPress by scanning the QR code below to install the corresponding build.

	App Name	WordPress
	Configuration	Release-Alpha
	Build Number	31391
	Version	PR #25353
	Bundle ID	org.wordpress.alpha
	Commit	f79ffdc
	Installation URL	429f5r081o8io

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📲 You can test the changes from this Pull Request in Jetpack by scanning the QR code below to install the corresponding build.

	App Name	Jetpack
	Configuration	Release-Alpha
	Build Number	31391
	Version	PR #25353
	Bundle ID	com.jetpack.alpha
	Commit	f79ffdc
	Installation URL	2a83ss7i96dao

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[wpmobilebot]

🤖 Build Failure Analysis

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[sonarqubecloud]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[kean]

I've tested the changes on one of my sites and was not able to get the new screens to show the hierarchy. In addition, some of the pages appear to be missing.

[kean]

(nit) I'd suggest extracting showSubdirectoryIcon and also extracting the two branches for flat/hierarchal data.

[kean]

The web version bails if there are too many pages. If a site has more than 100 pages, a hierarchal view would be unusable as it would require too much scrolling, so there is no point attempting to show the hierarchy as it would only make the user experience worse. For a site that has a large number of pages, this would also become a performance issue. wdyt about following how the web approaches it?