vegetation bin indexing

[rgknox]

Description:

This set of changes introduces some consistency improvements to how we determine the number of vegetation layers, and how we access and use those indices. Of note, the lower bound of this array has been changed to 0.

Collaborators:

@ckoven

Expectation of Answer Changes:

Not sure. This may be a bug fix as well. Looking again.

Checklist

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All checklist items must be checked to enable merging this pull request:

Contributor

• The in-code documentation has been updated with descriptive comments
• The documentation has been assessed to determine if updates are necessary

Integrator

• FATES PASS/FAIL regression tests were run
• Evaluation of test results for answer changes was performed and results provided

Documentation

• Technical Note update:
• User's Guide update:

Test Results:

CTSM (or) E3SM (specify which) test hash-tag:

CTSM (or) E3SM (specify which) baseline hash-tag:

FATES baseline hash-tag:

Test Output: