Add evalFold combinator to Stream

[Ivan091]

Thanks for opening a PR!

If the CI build fails due to Scalafmt, run sbt scalafmtAll and push the changes (generally a good idea to run this prior to opening the PR).

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[Ivan091]

Hi guys, my first PR ever to an Open Source lib.
Once in a while, I need this evalFold method, it's annoying we don't have it yet.
As a workaround I've been using evalMapAccumulate; though, it's not elegant

[mpilquist]

Awesome, thanks for contributing & congrats on your first PR to open source! Much appreciated!