Handle several RPCs provider at once

[peyha]

Is your feature request related to a problem? Please describe.
Using an Alchemy RPC is pretty difficult with Cryo even after fine-tuning the concurrency parameters. Half of the requests exceed the compute units per second capacity.

Describe the solution you'd like
One solution could be to allow users to enter several RPCs in the command (or in an env variable) and to make cryo dynamically change the RPC when it runs

Describe alternatives you've considered
I don't have my own node yet

Additional context
cryo is cool