Factor out HasOut common trait

[tovbinm]

Related issues
Following up on #269 - a sequence of PRs on allowing model loading without workflows...

Describe the proposed solution
Factored out common HasOut trait (similarly to HasIn that we have)

[codecov]

Codecov Report

Merging #272 into master will decrease coverage by 0.03%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #272      +/-   ##
==========================================
- Coverage    86.4%   86.36%   -0.04%     
==========================================
  Files         318      319       +1     
  Lines       10461    10431      -30     
  Branches      348      552     +204     
==========================================
- Hits         9039     9009      -30     
  Misses       1422     1422

Impacted Files	Coverage Δ
...stages/base/quaternary/QuaternaryTransformer.scala	100% <ø> (ø)	⬆️
...la/com/salesforce/op/stages/OpPipelineStages.scala	63.51% <ø> (-11.95%)	⬇️
...c/main/scala/com/salesforce/op/stages/HasOut.scala	100% <100%> (ø)

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[wsuchy]

OK