Fix constraints and names for new Foldable methods

[travisbrown]

This is a follow-up for #3084, with three changes, two of which should be uncontroversial:

• These are methods on the Foldable and Reducible type classes, and shouldn't have Foldable or Reducible constraints, so I've removed them.
• I fixed the references in the first @see clauses in the API docs for the Foldable methods (they should point to the *By methods on Reducible).

I've also changed the method names from minimumOptionBy and maximumOptionBy to minimumByOption and maximumByOption. This is consistent with the standard library's maxByOption, and also with e.g. reduceRightOption (from both the standard library and Cats).

Following the standard library here seems like the right thing to do, and these new methods haven't been in a release yet, so we don't need to worry about compatibility. If people would prefer to keep the OptionBy versions I can remove that commit, though.

/cc @joroKr21

[LukaJCB]

Good catch 👍

[kailuowang]

Thanks!

[codecov-io]

Codecov Report

Merging #3122 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master    #3122   +/-   ##
=======================================
  Coverage   93.17%   93.17%           
=======================================
  Files         372      372           
  Lines        7182     7182           
  Branches      198      198           
=======================================
  Hits         6692     6692           
  Misses        490      490

Flag	Coverage Δ
#scala_version_212	93.52% <100%> (+0.02%)	⬆️
#scala_version_213	90.85% <100%> (+0.01%)	⬆️

Impacted Files	Coverage Δ
core/src/main/scala/cats/Foldable.scala	100% <100%> (ø)	⬆️
core/src/main/scala/cats/Reducible.scala	100% <100%> (ø)	⬆️

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[joroKr21]

Ohh, I think I see what happened here. Initially added them as bincompat syntax I think, then realized we can have them in the typeclasses after dropping 2.11, but I completely forgot to remove the constraints.

I wonder if -Ywarn-unused:params would've helped here.
No it wouldn't they were actually used 😞

Regardless, thank you @travisbrown!

I'm ok with the name change as well.

[joroKr21]

Thank you!

[travisbrown]

@joroKr21 Ah, that makes sense!