Use cardano-node directly for creating nodes instead of cardano-testnet

[adithyaov]

See #164

The primary goal is to remove the use of pfctl.

Cascading effects:

• Address the use of sudo
• pfctl should have localised effect
• Add support for linux

[adithyaov]

Will close this issue after #169 is merged.
We want to do this later for more control. But let's close it for now and recreate the issue when required.