This question really raises several issues:

• Which is more important to product photography - Camera or lens?
• What are the advantages of a camera like the Canon 7D compared to the Canon Rebel T2i?
• What type of lens is most suitable for product photography?
• Is there a single type of lens suitable for both detail shots and wider views? That isn't a zoom lens?

The answer to the first is: neither. In terms of gear, lighting is by far the most important element for product photography. Lenses are next, and what type of camera you use is a very distant third.

As for the second, please see this answer to another question. The 7D is faster handling and more durable. But with product photography you're probably going to shoot more methodically and use magnified Live View to focus manually, so a lot of that faster handling speed doesn't necessarily apply to product photography.

There really is no specific answer to the third question. It all depends on what kind of products you are photographing, how large and/or small they are, how much room you have in your studio, etc. In general, prime lenses give more affordable performance in terms of optical quality than zoom lenses. The best and most expensive zoom lenses deliver about the same optical quality as primes often costing one-fifth as much or even less. Then there are the expensive primes...

And lastly, it depends. If you have enough space you could use something like an EF-S 60mm f/2.8 Macro. The 60mm focal length provides the same field of view on an APS-C body that a 100mm lens provides on a full frame camera. You would use the macro capabilities to get in close for those detail shots. Note that using a macro lens requires a lot of good, soft light coming from multiple directions to avoid creating shadows with the camera/lens in so close. And any macro lens will increase the effective aperture for the same f-number setting when using high magnification ratios.

You could then shoot your wider views from further back. At more regular focus distances macro lenses don't loose effective aperture the way they do at high magnification levels. If you don't have enough space to back up that far or don't prefer the compressed look that you will get shooting your full product shots from a longer distance, you would then need a wider angle lens that would allow you to get the perspective of shooting from closer to the products. Your existing kit lens would be suitable for the full product shots in that case.