Rename rangeE for clarity

[travisbrown]

This is one small thing that I just noticed in #3150, but I'd already caused enough trouble there so I decided it'd be best to handle in a follow-up. 😄

I think rangeE was named to match range, but it doesn't actually create a range, and it's not in any way Either specific, so I replaced it with a general fromValues method that can be used in these tests.

[codecov-io]

Codecov Report

Merging #3198 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #3198   +/-   ##
=======================================
  Coverage   93.06%   93.06%           
=======================================
  Files         376      376           
  Lines        7409     7409           
  Branches      196      196           
=======================================
  Hits         6895     6895           
  Misses        514      514

Flag	Coverage Δ
#scala_version_212	93.39% <ø> (ø)	⬆️
#scala_version_213	92.83% <ø> (ø)	⬆️

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