Merge individual package branches to `main`

[dshemetov]

Since this repo is no longer supporting active development of multiple packages, we could make a move to consolidate the individual package branches to main. This would help mitigate recent issues with breaking CI/tests that get fixed in one package branch, but not in others.

• evalcast - Use reframe() instead of summarize() for multiple rows #620
• modeltools - Merge modeltools into main #630

We could choose to keep these package branches around or remove them. If we keep them around, then it might be good to make a GH action that merges back from main into the package branch, so everything stays synced. If we don't, then some downstream code (mostly production forecasting) would need to update github refs.