Update site transients response differences

[krotz]

Why do the update_themes and update_plugins have a different response type, one is an stdObject another is a simple array.

That being said the plugin and theme upgrader have the same discordance. Please make them so they are consistent with one another.

[nacin]

This is indeed super annoying but I'm not sure we can change it very easily, without moving to some kind of update response object that implements ArrayAccess.