feat: add a new ternary contour plot operator

[ELin2025]

What changes were proposed in this PR?

This change relates to the addition of a ternary contour plot operator, which visualizes how a scalar value varies as a function of three normalized components that sum to a constant (typically 1 or 100%).

In a ternary contour plot:

• Each vertex of the triangular plot represents 100% of one component.
• Any interior point represents a mixture of the three components.
• Contour lines or color gradients indicate equal values of the measured quantity across different mixtures.

This visualization is useful for identifying regions where the output is optimized or insensitive to changes in the component proportions, as well as for understanding trade-offs between the three variables.

The operator takes in 4 inputs. The first three variables are the components, and the fourth variable is the output that corresponds to the proportion of the the three components.

Any related issues, documentation, discussions?

Needs python library scikit-image
Can be installed using: pip install scikit-image

How was this PR tested?

Tested with existing test cases

Was this PR authored or co-authored using generative AI tooling?

No