[Proposal] Consider an alternative approach to `.env` files.

[d0cd]

.env configurations are unwieldy especially when you have multiple roles.

While PRIVATE_KEYs should be hidden, it doesn't make much sense to have the network or endpoint an a hidden config. These could be moved to program.json

We could also consider something like profiles managed by the Leo CLI to make managing configs easier.

[mohammadfawaz]

I'm in favour of moving network and endpoint to program.json as a first step.