Packet: deployment flexibility at start time

[vielmetti]

What would be helpful (if it isn’t already available) is to be able to configure cross-cloud for Packet to select some variables at launch time (e.g. master machine type, worker machine type, coreos version, data center) so that we could repoint the tests to another data center / machine combo without a total rebuild.

The current provisioning is e.g. hardcoded to SJC1, but someone might reasonably want to try in EWR1; or to use a different machine type for the worker for capacity or testing reasons.