[Draft] Perform VoI analysis

[Value of Information in Influence Diagrams and LIMIDs](https://github.com/equinor/prisma-decision-docs/blob/voi/domain/voi.md)

Start by reading the linked domain/voi.md document in the voi branch, which describes Value of Information in Influence Diagrams and LIMIDs. Use it to determine the required analysis scope and how it should fit into prisma-decision-api; done is an implemented VoI analysis matching that document, with tests or other acceptance checks identified during the design.

Written by the indexing model from the issue text.