Fix iframe error when accessing Add new Page on post command palette

[epeicher]

Related to #93979

Proposed Changes

• Add two new handlers to post messages for Add new post and Add new page to the calypsoify-iframe to avoid iframe errors
• The new handler will handle the Add new page and Add new post commands in the Command palette

Why are these changes being made?

• To fix the IFrame error described in Accessing "New Page" via the Command Pallete While Writing a Post in Calypso Causes "Refused to display (..) 'X-Frame-Options' to 'sameorigin'" error #92634 #93979

Testing Instructions

• Execute cd apps/wpcom-block-editor/ && yarn dev --sync
• Sandbox your simple site and widgets.wp.com
• Apply this patch and navigate to your local edit post page, http://calypso.localhost:3000/post/<your simple site>, e.g. http://calypso.localhost:3000/post/mytestsimplesite.wordpress.com
• Open Command Palette by clicking on the top bar or pressing Cmd+K
• Select Add new page or Add new post
• Check you are correctly redirected and no iframe errors are displayed

Pre-merge Checklist

• Has the general commit checklist been followed? (PCYsg-hS-p2)
• Have you written new tests for your changes?
• Have you tested the feature in Simple (P9HQHe-k8-p2), Atomic (P9HQHe-jW-p2), and self-hosted Jetpack sites (PCYsg-g6b-p2)?
• Have you checked for TypeScript, React or other console errors?
• Have you used memoizing on expensive computations? More info in Memoizing with create-selector and Using memoizing selectors and Our Approach to Data
• Have we added the "[Status] String Freeze" label as soon as any new strings were ready for translation (p4TIVU-5Jq-p2)?
• For changes affecting Jetpack: Have we added the "[Status] Needs Privacy Updates" label if this pull request changes what data or activity we track or use (p4TIVU-aUh-p2)?

[github-actions]

Calypso Live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-118133

Jetpack Cloud live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-118133&env=jetpack

Automattic for Agencies live (direct link)

https://calypso.live?image=registry.a8c.com/calypso/app:build-118133&env=a8c-for-agencies

[matticbot]

This PR modifies the release build for the following Calypso Apps:

For info about this notification, see here: PCYsg-OT6-p2

• wpcom-block-editor

To test WordPress.com changes, run install-plugin.sh $pluginSlug add/new-page-command-calypsoify on your sandbox.

[matticbot]

This PR does not affect the size of JS and CSS bundles shipped to the user's browser.

Generated by performance advisor bot at iscalypsofastyet.com.

[xavier-lc]

@epeicher I've extracted the duplicated code into handleWpAdminRedirect.

[xavier-lc]

Works as described 👌

[epeicher]

@epeicher I've extracted the duplicated code into handleWpAdminRedirect.

Thanks @xavier-lc , great refactoring, much more generic