Stress test validators using linera benchmark

[ndr-ds]

Right now running linera benchmark doesn't really generate enough throughput to really stress test a validator. The end goal of this task is to be able to spin up a temporary network with lineractl, then run linera benchmark against it in a way that it should use up a lot of the local machine's resources in sending requests to the network.
Even so, we might not be able to actually exhaust CPU usage in the network from a laptop, so also being able to run this from GCP would be ideal (deploy something on GCP that will stress test a specific network)

• Subsequent linera benchmark runs take too long #3089
• Create continuous mode for linera benchmark #3090
• Paralellize continuous mode #3091
• Parametrize continuous mode #3092
• Run continuous mode from GCP VM with more resources #3093
• Try to find network bottlenecks under heavy load #3094
• Look into potential ways of doing actual "traffic generation" #3095