Update torch

[ElliottKasoar]

Resolves #312 and #328

Following astral-sh/uv#11323, we are able to properly set the MLIPs that require dgl as conflicting with chgnet.

By default, this currently means that torch will be updated to 2.5.1, (I added torch<2.6 for now, as a few things seemed to break), and we only revert to the pinned torch==2.2 when either matgl or alignn are requested.

I also changed all to exclude matgl or alignn, as there is no way to include the conflicting MLIPs, and I hope others we add soon will be compatible with newer torch versions, but the name could potentially be clearer, and we may want an equivalent for dgl MLIPs.

This also adds a bit more installation guidance, most of which is relevant to describing how you would go about upgrading torch/dgl, if you wanted to use all of the MLIPs still, but in theory some of that section could be split out into a separate PR, addressing #397.

To do:

• Fix tests
  • We'll need to install and test the dgl dependencies separately
• Add more developer guidance e.g. for testing?

[ElliottKasoar]

Note: will require resolution of astral-sh/uv#11479

[ElliottKasoar]

I rewrote the developer tutorial to focus on orb, since it's a bit more standard than alignn now, and also did a quick pass to update places in the docs which assumed MACE was installed (it's still required for testing, though).