Parameter for default volume IOPS + provisioned throughput

[richardstephens]

Is your feature request related to a problem? Please describe.
When debugging some slow builds, we've noticed that some of our builds seem to be IO constrained.

Describe the solution you'd like
We'd like it to be possible to configure the provisioned IOPS and throughput for the EBS volume as a parameter in the template, similar to how we configure volume size today

Describe alternatives you've considered
We could edit the template, but we would prefer to avoid modifications if possible as it makes upgrading more hassle.

We are looking into if it's possible to re-configure the provisioned throughput for the volume in the agent bootstrap script, but this is a suboptimal solution because it requires granting additional permissions to the IAM roles of the agent

Additional context
N/A