Mass balance BMI protocol implemented

[hellkite500]

Implement a basic mass balance BMI protocol which exposes cumulative mass balance terms via the BMI for consumption by some caller.

Additions

• A set of utility functions for implementing the ngen bmi protocol
• A new mass balance variable for potential (future) leakage terms, needed to implement the required ngen protocol

Removals

Changes

• Adjustments to CFE's run semantics to ensure storage in the domain is accumulated properly each time step
• Properly initialize various mass balance variables

Testing

1. Local unit tests pass
2. Checked with an initial prototype version of the model engine protocol

Checklist

• PR has an informative and human-readable title
• Changes are limited to a single goal (no scope creep)
• Code can be automatically merged (no conflicts)
• Code follows project standards (link if applicable)
• Passes all existing automated tests
• Any change in functionality is tested
• New functions are documented (with a description, list of inputs, and expected output)
• Placeholder code is flagged / future todos are captured in comments
• Project documentation has been updated (including the "Unreleased" section of the CHANGELOG)
• Reviewers requested with the Reviewers tool ➡️

Testing checklist

Target Environment support

• Linux
• MacOS

[hellkite500]

I'm not sure why GitHub is showing so much change on this file, but its really only these three lines (127-129)...

[PhilMiller]

Hiding vs showing whitespace seems to resolve it, so there's probably something in the diff that's whitespace-ish setting it off.

[hellkite500]

I noticed parts of this code has carriage returns on some line endings, so that's probably why...