Replace {RCurl} with {curl}

[infotroph]

This is a replacement for #2786, in which @moki1202 made a good start on replacing all calls to the RCurl package with the closest equivalents from the (newer, better designed, more actively maintained) curl package. I'm continuing the work here rather than in that branch because I gave him such bad advice about both RCurl and about git that it became my problem to fix it 😉 🙈

Still in progress, but pushing as a draft for visibility. Please squash-merge when it's time.

Description

Motivation and Context

Review Time Estimate

• [ ] Immediately
• [ ] Within one week
• [ ] 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.
• [ ] I have read the CONTRIBUTING document.
• [ ] I have added tests to cover my changes.
• [ ] All new and existing tests passed.

[infotroph]

Leaving two usages of RCurl in gSSURGO.Query because they conflict with changes in #2964. Will include the conversion of those are part of that PR.

[infotroph]

Ready for review. Please squash when merging.