Improving test coverage for `PEcAn.settings` package

[meetagrawal09]

Description

This PR aims to improve test coverage for the PEcAn.settings package (also fixes #3170)

Review Time Estimate

• [ ] Immediately
• [ ] Within one week
• [X] When possible

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• [ ] My change requires a change to the documentation.
• [ ] My name is in the list of CITATION.cff
• [ ] I have updated the CHANGELOG.md.
• [ ] I have updated the documentation accordingly.
• [X] I have read the CONTRIBUTING document.
• [ ] I have added tests to cover my changes.
• [X] All new and existing tests passed.

[meetagrawal09]

@infotroph, @mdietze I have completed adding tests for all the functions in the PEcAn.settings package. Would like to get a review on the PR.

[allgandalf]

hey @meetagrawal09 , can you please sync your branch with the develop branch of the main repository? The CI pipeline has been updated today, so the required checks will only be initiated when you sync your fork with the latest develop branch.