Port old API tests for products

Make module `test_product_v2` accomplish the same goals as module
`test_product`. Remove the latter module and update the API documentation
accordingly.
> is there a reason for not including all char types (missing are `cjk` and `latin-1`) for both `name`

There were existing tests for updating a product's name using alpha, alphanumeric and numeric charsets. I left them essentially alone. Is there any particular reason for omitting cjk and latin-1 charsets? I have no idea. I'll try updating this.

> and `description`?

The old API tests included exactly one test which updated a product's description. I ported it over pretty much verbatim.