Make "testnet scenarios" available for TeCI

Find a way of running the binary added in tezos!7634 (merged) in TeCI.

Possible solutions:

• adding the binary in the tezos/tezos docker image. I started a draft here: tezos!7830 (closed)
• add the binary produced in the tezos/tezos ci to its artifacts. then, inside teci, fetch the binary from there on each execution