[Blueprints] Preserve more error information on failed fetch

[adamziel]

Motivation for the change, related issues

Before this PR a failed fetch would only print surface level error:

 [WordPress Server Child] Failed to start server: Error: Error when executing the blueprint step #3 ({"step":"installPlugin","pluginData":{"resource":"wordpress.org/plugins","slug":"woocommerce"}}) : Could not download "https://downloads.wordpress.org/plugin/woocommerce.latest-stable.zip".

After this PR a failed fetch includes the original error cause and provides the full error information including the original stack trace.

Implementation details

Just adds { cause: error }