Sphinx wishlist

[arthurpaulino]

While our proving pipeline is still evolving, let's use this issue to list things that don't spark joy on the Sphinx's prover.

Note: please, only mark items as resolved once the change is done on Sphinx and successfully integrated on this repo.

• There shouldn't be a requirement for one chip to be called "CPU"
• There shouldn't be a requirement for at least one chip to produce a preprocessed trace
• ShardingConfig should not be required to be Default. The fact that Sphinx initializes a default instance (using env vars) is an obscure hack that leads to multiple headaches
• Trace generation should not happen twice