Adding models RD, EN, ET, Stacking, GB, AB, MultiOutput(only for multiple output benchmarks) to all benchmarks

[ShamanthShastry]

PR Description

This change was done to add 6 (and in some cases, 5) more models to be compared in benchmarks BWR Micro Core, Critical Heat Flux (CHF) Prediction, Heat Conduction, Fuel Performance, Reactor Physics, and Rod Ejection.

Closes: #75

Models Added

• RD
• EN
• ET
• Stacking
• GB
• AB
• MultiOutput (only in benchmarks handling multiple outputs)

Changes Made

• The above models were added into lists in Model Initialization and Model Postprocessing, along with numerous corresponding hyperparameters added in Initialization and Tuning.

Unit Testers: @myerspat

(Note: pending a run of the code due to my system's issues)