Support for testnet4 on test environment

[thiagorb]

Is your feature request related to a problem? Please describe.
The testnet3 seems to be deprecated, and starting a new node in it takes a lot of time, since it is already in block 4M+.

Describe the solution you'd like
I guess there should be a transition period where both networks are available, in case there are people using the test environment with testnet3, but from what I could see, there is not much going on, on the test systems.