Test AWS Graviton instances in the fleet (t4g.medium)

[zah]

The AWS Graviton instances are some of the cheapest on-demand servers on AWS, but they may provide adequate performance for running Nimbus. t4g.medium in particular is a 2 vcpu, 4 GB RAM instance that seems to be a good candidate.

If we get good results from such servers on our own testnet fleets, we will be able to make some good recommendations to all potential Nimbus users who would like to base their operation on AWS.

[jakubgs]

Since that host has 4 GB of RAM we can't build the node on it. The only practical solution aside form making a new CI setup for building ARM builds of unstable, testing, and stable is to deploy a release and use prebuilt binaries.

Based on what @zah said in chat, since this is just an experiment we can use release builds for now.