Vacuumlabs fracada audit findings remediation

[kocisevic-vl]

• Plutus version was updated.
• Script architecture was updated to enable some fixes, mainly the introduction of the validity token.
• Offchain code was maintained and kept in line with the changes and the new architecture.
• Tests were maintained and kept in line with the changes and the new architecture.
• New tests for audit findings are added to show that they were failing before our changes and are passing with them.
• Everything else (demo, release and scripts folders) wasn't necessary to fix audit findings and wasn't maintained or updated.