Implement the Duplicate post action

[crazytonyli]

Description

Fixes https://linear.app/a8c/issue/CMM-1975

The "Duplicate" action is implemented as opening a post editor with another post's content and some basic settings (categories and post format, which follows the existing duplicating AbstractPost behaviour). Nothing is saved, neither locally nor remotely.

[dangermattic]

	1 Warning
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Generated by 🚫 Danger

[sonarqubecloud]

Quality Gate passed

Issues
6 New issues
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

[wpmobilebot]

📲 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	31718
	Version	PR #25440
	Bundle ID	org.wordpress.alpha
	Commit	0d06220
	Installation URL	0bngnnq0tu568

Automatticians: You can use our internal self-serve MC tool to give yourself access to those builds if needed.

[wpmobilebot]

📲 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	31718
	Version	PR #25440
	Bundle ID	com.jetpack.alpha
	Commit	0d06220
	Installation URL	7jlpiu853vm50

Automatticians: You can use our internal self-serve MC tool to give yourself access to those builds if needed.