Adding implementation details to tags in globalFlux

[zachmprince]

What is the change?

This is adding details of the implementation in the .. impl:: tags within globalFlux. Most of them are adding paragraphs. A couple of them I simply put the Notes section in the doctring under the tag to avoid duplicate information.

Why is the change being made?

This is part of on-going QA work.

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Checklist

• This PR has only one purpose or idea.
• Tests have been added/updated to verify that the new/changed code works.

• The code style follows good practices.
• The commit message(s) follow good practices.

• The release notes (location doc/release/0.X.rst) are up-to-date with any important changes.
• The documentation is still up-to-date in the doc folder.
• If any requirements were affected, mention it in the release notes.
• The dependencies are still up-to-date in pyproject.toml.

[CLAassistant]

All committers have signed the CLA.

[john-science]

I am "Approving" in Tian's place, as GH doesn't seem to recognize her account?

TBD. We'll fix that.