#1704/#1705 weighted decision selection

[ghost]

Description

When a profile contains a decision (if constraint) which refers to weighted set values, currently the generator doesn't take the weightings into account.

Changes

• Update the decision selection logic to apportion a weighting to each branch of a decision
• Use this weighting when randomly selecting a value for the decision, so that values are projected as per their weightings

Additional notes

Issue

Resolves #1704 Resolves #1705