Add redeem and redeemWith

[travisbrown]

This PR includes @alexandru's first commit from #2237 but removes the EitherT enhancements and focuses on the part that fixes #2161 (new redeem and redeemWith methods).

See typelevel/cats-effect#191 for additional discussion.

I still think we should try to get the EitherT improvements merged, but redeem seems like a higher priority for 2.1.0. I've also reverted some other changes in the original commit in order to preserve binary compatibility.

Note that I've moved redeem from MonadError to ApplicativeError and have added syntax and syntax tests.

[codecov-io]

Codecov Report

Merging #3146 into master will decrease coverage by 0.02%.
The diff coverage is 84.84%.

@@            Coverage Diff             @@
##           master    #3146      +/-   ##
==========================================
- Coverage   93.28%   93.25%   -0.03%     
==========================================
  Files         376      376              
  Lines        7323     7343      +20     
  Branches      195      186       -9     
==========================================
+ Hits         6831     6848      +17     
- Misses        492      495       +3

Flag	Coverage Δ
#scala_version_212	93.58% <84.84%> (-0.04%)	⬇️
#scala_version_213	90.9% <84.84%> (-0.05%)	⬇️

Impacted Files	Coverage Δ
core/src/main/scala/cats/syntax/monadError.scala	88.88% <0%> (-11.12%)	⬇️
.../src/main/scala/cats/syntax/applicativeError.scala	94.44% <0%> (-5.56%)	⬇️
core/src/main/scala/cats/instances/either.scala	100% <100%> (ø)	⬆️
core/src/main/scala/cats/ApplicativeError.scala	100% <100%> (ø)	⬆️
...n/scala/cats/laws/discipline/MonadErrorTests.scala	100% <100%> (ø)	⬆️
core/src/main/scala/cats/instances/option.scala	98.27% <100%> (+0.12%)	⬆️
...a/cats/laws/discipline/ApplicativeErrorTests.scala	100% <100%> (ø)	⬆️
laws/src/main/scala/cats/laws/MonadErrorLaws.scala	100% <100%> (ø)	⬆️
...rc/main/scala/cats/laws/ApplicativeErrorLaws.scala	100% <100%> (ø)	⬆️
core/src/main/scala/cats/MonadError.scala	100% <100%> (ø)	⬆️
... and 2 more

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[LukaJCB]

LGTM, thanks! :)

[rossabaker]

Delighted to see this one arrive.