Diffusive fortran kernel correctly executes diffusive wave on stream segments defined by Python preprocessing

[kumdonoaa]

When defining diffusive domain including not only mainstem but also connected tributaries by this config file, diffusive.f90 hasn't been executed diffusive wave routing on all the reaches where the config file defines to run diffusive wave on. That's because diffusive.f90 assumes a reach without any its upstream reach to not run diffusive wave on but instead to already have given flow and depth data computed from other routing model, in this case MC. By defining a reach of index j in frnw_g with specified value, for example, 555 for diffusive reach while -555 for already-computed reach, diffusive.f90 now correctly route on all reaches told to run diffusive wave.

Additions

AbstractRouting.py: Select a single cross section topo data with minimum value of cs_id for each stream segment
diffusive_utils_v02.py: Decide a stream reach of index j whether to run diffusive wave or not to run diffusive but have already-computed flow value by MC instead.
diffusive.90: Implement diffusive wave on all the reaches that are told to run diffusive on.

Removals

Changes

Testing

Screenshots

Notes

Todos

Checklist

• PR has an informative and human-readable title
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Testing checklist

Target Environment support

• Windows
• Linux
• Browser

Accessibility

• Keyboard friendly
• Screen reader friendly

Other

• Is useable without CSS
• Is useable without JS
• Flexible from small to large screens
• No linting errors or warnings
• JavaScript tests are passing

[JurgenZach-NOAA]

When mainstem: 'mainstem' is included in the yaml file, it runs.

[JurgenZach-NOAA]

Code runs, recommend mainstem: 'mainstem' in all test examples now.