Untangling Calypso: Avoid Multiple Redirection from the Admin Bar

[Copons]

On Untangled sites, we should update the "New" items in the Admin Bar to point directly to the relevant wp-admin screen (as long as untangled).

We should ensure the behaviour is the same on non-Untangled sites with the interface set to Classic/wp-admin.
AFAICS, the New -> Post link points to the Calypso editor and then redirects to /wp-admin/post-new.php?post_type=post&calypsoify=1.

[github-actions]

OpenAI suggested the following labels for this issue:

• [Feature Group] Content Management: The issue pertains to managing content links in the Admin Bar, which directly relates to how admins handle their site's content.
• [Feature] Calypso & wp-admin Navigation: The issue discusses navigation issues between Calypso and wp-admin, specifically concerning redirections that affect user flow.
• [Feature] Classic Interface: The body mentions the interface set to Classic/wp-admin, indicating its relevance to the behavior being discussed.