Post Trash: Add confirmation dialog and correct trash support check

[UmeraGhori]

What:
This PR adds a confirmation dialog to the "Move to trash" button in the post editor. This ensures users do not accidentally delete posts or pages.

Technical Changes:
Based on previous feedback, I have also refactored how we check if a post type supports the 'trash' feature.

• Previously: Attempted to check disableTrash in editor settings (which was incorrect).
• Now: Properly retrieves the post type entity via the @wordpress/core-data store and checks postTypeEntity.supports.trash.
• Replaced string literals for store selection with proper store imports to comply with linting standards.

Why:

• Improves User Experience (UX) by preventing accidental data loss.
• Ensures the code relies on the correct source of truth (Core Data Entity) for post type capabilities.

How to Test:

1. Open any Post or Page in the Block Editor.
2. Navigate to the "Summary" panel in the settings sidebar.
3. Click the "Move to trash" button.
4. Verify that a confirmation modal appears:
   • If the post supports trash: It asks to "Move to trash".
   • If the post does not support trash: It asks to "Delete permanently".
5. Confirm that the action only completes after clicking the confirm button inside the dialog.

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Co-authored-by: UmeraGhori <[email protected]>
Co-authored-by: Mamaduka <[email protected]>
Co-authored-by: t-hamano <[email protected]>
Co-authored-by: hbhalodia <[email protected]>

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[UmeraGhori]

@Mamaduka @t-hamano Thanks for the guidance on the previous approach.

I have updated the code to use the core store to check for trash support (postTypeEntity.supports.trash) instead of editor settings. I've also fixed the linting errors. Could you please take a look?

[Mamaduka]

To my knowledge, and somewhat similar to the proposed solution in #74265, the postTypeEntity.supports.trash settings flag doesn't exist.

If the proposal introduces a new support flag that differs from the suggestions in the original issues, it must be documented in the description.

For now, I think it would be best to move the discussion back to the issue until there's a clear resolution path.

[UmeraGhori]

Thanks for the review @Mamaduka.

You are right — I was operating under the assumption that the trash support flag from register_post_type (PHP) was exposed in the REST API supports object. Since that flag doesn't exist in the frontend settings, I agree that we need to define the correct resolution path first.

I will pause this PR and move the discussion back to the issue thread to determine the best way to handle this check.

[Mamaduka]

@UmeraGhori, the problem is that the supports.trash flag doesn't exist, so of course it's not exposed anywhere. Let's continue the discussion on the issue. If you're unsure about your solution, it's always okay to ask.