What term or phrase could be used to describe everything that is necessary for a successful product, except for the product itself?

Solution 1:

ancillary products: ancillary, defined by The Free Dictionary :

Auxiliary or accessory: an ancillary pump.

Something that is subordinate or accessory to something else: a tripod, battery charger, and other camera ancillaries

Another possibility is supporting products or all items necessary for product support. I don't find a reference for supporting products, but product support is defined by Wikipedia

Product support is a service provided by many retailers of various products, primarily electronics, that provides the end-user with a resource for information regarding the product, and help if the product should malfunction. Product-support information can be found in most manuals for products via a phone number, web site address, or physical location

This definition stresses services, but it does mention a manual and maybe the sense could be stretched to cover the items the OP listed.

(Note that they are not by-products or co-products. By-product; co-product)

Solution 2:

You could call them accessories.

Accessory noun A thing which can be added to something else in order to make it more useful, versatile, or attractive: optional accessories include a battery charger and shoulder strap - ODO