Replace assert with require

[tovbinm]

Related issues
Assertion checks assert can be removed from the compiled byte code if there happen to be a flag -Xdisable-assertions set at compile time.

Describe the proposed solution
Replace assert with require everywhere in main code + update the tests.

Describe alternatives you've considered
N/A

Additional context
https://www.scala-lang.org/api/current/scala/Predef$.html

[tovbinm]

@vpatryshev

[codecov]

Codecov Report

Merging #159 into master will increase coverage by 0.01%.
The diff coverage is 96.55%.

@@            Coverage Diff             @@
##           master     #159      +/-   ##
==========================================
+ Coverage   85.75%   85.76%   +0.01%     
==========================================
  Files         303      303              
  Lines        9912     9912              
  Branches      337      543     +206     
==========================================
+ Hits         8500     8501       +1     
+ Misses       1412     1411       -1

Impacted Files	Coverage Δ
...sforce/op/utils/spark/OpVectorColumnMetadata.scala	75.55% <100%> (ø)	⬆️
.../op/stages/base/sequence/SequenceTransformer.scala	100% <100%> (ø)	⬆️
...e/op/stages/impl/feature/SmartTextVectorizer.scala	97.4% <100%> (ø)	⬆️
...e/op/stages/impl/insights/RecordInsightsCorr.scala	98.24% <100%> (ø)	⬆️
...sforce/op/stages/impl/feature/Transmogrifier.scala	96.74% <100%> (ø)	⬆️
...m/salesforce/op/stages/OpPipelineStageParams.scala	91.17% <100%> (ø)	⬆️
...p/stages/impl/feature/SmartTextMapVectorizer.scala	100% <100%> (ø)	⬆️
...force/op/stages/impl/feature/OpStringIndexer.scala	100% <100%> (ø)	⬆️
...scala/com/salesforce/op/features/FeatureLike.scala	41.93% <100%> (ø)	⬆️
...stages/base/sequence/BinarySequenceEstimator.scala	100% <100%> (ø)	⬆️
... and 9 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 8264265...86063fa. Read the comment docs.