Added_NWM_ponded depth

[ajkhattak]

The PR adds NWM_PONDED_DEPTH variable to the BMI variables output list. It represents surface water, stored in the GIUH/NASH_Cascade array, that didn't drain during the current timestep. It will be need for NextGen vars parity with NWM variables.

Additions

• Added a BMI output variable

Removals

• None

Changes

• None

Testing

1. All existing tests pass and results are unchanged

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)
• Passes all existing automated tests
• Any change in functionality is tested
• New functions are documented (with a description, list of inputs, and expected output)
• Reviewers requested with the Reviewers tool ➡️

[madMatchstick]

@ajkhattak - I don't see any problems with these updates, at least in terms of functionality. We may have to eventually update the example realization(s) in ngen/data dir?

Do you recommend running any additional local tests/coupling? -thx!

[ajkhattak]

@madMatchstick I don't think we need more testing here, this NWM_Ponded_depth will only be needed/used in baseline simulations.