Don't reuse global model params

[hellkite500]

Fixing bug in reuse of global model_params when linking external data from a global formulation definition

Changes

• Copy global formulation config before modifying with link_external

Testing

1. Tested on realization provided in #871 and ensured each feature on the BMI receiving end has correct area values

Checklist

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

Target Environment support

• [x] Linux
• [x] MacOS