Layer and DomainLayer Formulation Management

[hellkite500]

Supporting model layers which don't have a 1-1 model -> catchment association requires additional configuration and management. This PR addresses 3 key components for supporting model layers.

1. Refactoring of layer configuration parsing
2. Creation of layer formulation attaching a model formulation to the layer
3. A DomainLayer abstraction which associates a single formulation with the entire simulation domain (hydrofabric) instead of a subset of catchment features.

Additions

• DomainLayer subclass of the Layer abstraction
• ngen::config::Layer for parsing layer configurations
• Formulation_Manager attribute and functions for managing "Domain Layer" formulations.

Removals

Changes

• Refactored parsing in Formulation_Manager using the ngen::config::Layer structure
• Refactored main in Ngen.cpp to support creation of DomainLayers and

Testing

1. This work was used in testing the initial NOM gridded model runs via ngen. Additional unit/integration testing should be added.

Todos

• A couple of TODO's and FIXME's are noted in the code. The FIXME particularly in the case of parsing Layer configurations with invalid configurations should likely be addressed before merging. This should likely throw a std::runtime error as used in some other config parsing when required missing keys are not found. I'll try to get this added ASAP while the other components are being reviewed. FIXME addressed in 88f3d23

• Need to add some unit test code as well.

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 ➡️

Target Environment support

• Linux
• MacOS

[aaraney]

Its for sure worth noting here and in the constructor description a DomainLayer's relationship with NextGen's concept of a nexus.

[hellkite500]

addressed in 291900e

[PhilMiller]

Typo 'Determines'

[hellkite500]

fixed in 88f3d23

[PhilMiller]

This is duplicated from formulation initialized just above on line 104

[hellkite500]

removed duplicate in 581e8e5

[hellkite500]

Would be beneficial to have this merged before #744 is ready for review/merge. After talking with @donaldwj about the netcdf semantics, we are going to tie those to the Layer abstraction and hook into the Formulation to get variable meta data. With these, we should have enough information to create the netcdf dimensions needed and look to efficient array writes to the output files based on the feature sets of a given layer.

[program--]

Just a few typos, but once those are fixed it looks good to me.