Add node code lists R17 and R20

[SiddharthJoshi-Git]

This PR adds two new regional mappings for GUIDE project and YSSP'23 work related to it. The R17 regional mapping is for YSSP work and R20 for overall GUIDE project.

How to review

• Read the diff and note that the CI checks all pass.
• Confirm the new lists appear in the documentation.
• More TBA.

PR checklist

• [ ] Continuous integration checks all ✅

• [ ] Add or expand tests; coverage checks both ✅
• [ ] Add, expand, or update documentation.

• [ ] Update doc/whatsnew.

[khaeru]

@SiddharthJoshi-Git, thanks for starting this PR.

• I updated the PR description, in particular to re-add the "PR checklist," which is not optional. Please re-read the comments inline to understand how to use ~strike through~ if you think a particular item should not be needed for a certain PR (though in this case, I think all are relevant).

As next steps, you should:

• Bring your branch up to date with iiasa:main. You can use the provided button above: "Update branch > update with rebase" (and then git pull --rebase on your local system to mirror the changes).
• Look at the checks/tests that are failing. (Click the "Details" next to the failing jobs.) Try to make a guess as to why, and if possible adjust or expand the tests so that they pass.

[SiddharthJoshi-Git]

@SiddharthJoshi-Git, thanks for starting this PR.

• I updated the PR description, in particular to re-add the "PR checklist," which is not optional. Please re-read the comments inline to understand how to use ~strike through~ if you think a particular item should not be needed for a certain PR (though in this case, I think all are relevant).

As next steps, you should:

• Bring your branch up to date with iiasa:main. You can use the provided button above: "Update branch > update with rebase" (and then git pull --rebase on your local system to mirror the changes).
• Look at the checks/tests that are failing. (Click the "Details" next to the failing jobs.) Try to make a guess as to why, and if possible adjust or expand the tests so that they pass.

HI @khaeru,

The 'ALL' tests are failing due to licensing error from GAMS. As per some suggestions I received, can this be due to me starting a PR from my fork. Should I restart a PR by making a branch within the message_ix_models (IIASA) to remedy the licensing errors?

Best, Sid

[khaeru]

Should I restart a PR by making a branch within the message_ix_models (IIASA) to remedy the licensing errors?

Yes, that sounds like a good idea. A nice branch name to use would be something like enh/node-R17-R20 (for "enh"ancement).

You can copy the raw Markdown from this PR's description into the new one; saves re-writing.