19215: Adds initial version of terraform code for multi-host deploy in AWS.

19215: Adds initial version of terraform code for multi-host deploy in AWS.

It's separated in 3 sections: vpc, data-storage & services. This is to limit
the 'blast radius' of a potential error when applying changes, as recommended
in many places.
Each state should be applied in the order described above, and their outputs
feed the following states with important data.
The shared 'terraform.tfvars' file allows the operator to customize their
deployment.

Arvados-DCO-1.1-Signed-off-by: Lucas Di Pentima <lucas.dipentima@curii.com>