Threat of plutus-apps getting obsolete

[szg251]

There's a possibility that plutus-apps (PAB) will not be supported in the future, so we might need to maintain it ourselves, or move away from it altogether.
This could potentially be a good moment to refactor some of our code, once we don't need to conform to the interface of plutus-apps.

[t4ccer]

BPI uses patched plutus-apps so we would also get benefit of not having to patch future versions