#803 - add eval udf implementation - includes / requires #804

[chris-twiner]

This can be merged instead of #804 / #805, it requires the functionality.

per #803 any expression that needs further optimisation before compilation (like ExpressionProxy) fails when used in a UDF if they throw on doCodeGen.

This PR implements the expected Spark pattern of eval eval'ing. It requires the correct type derivation from #804 for both Seq and Set in order to work (due to MapObjects difference in eval vs compilation)

[codecov]

Codecov Report

Attention: Patch coverage is 95.95960% with 4 lines in your changes are missing coverage. Please review.

Project coverage is 95.56%. Comparing base (0fb9c58) to head (e157cdb).

Files	Patch %	Lines
...taset/src/main/scala/frameless/functions/Udf.scala	93.10%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #806      +/-   ##
==========================================
+ Coverage   95.46%   95.56%   +0.09%     
==========================================
  Files          67       68       +1     
  Lines        1257     1329      +72     
  Branches       42       45       +3     
==========================================
+ Hits         1200     1270      +70     
- Misses         57       59       +2     

Flag	Coverage Δ
2.12-root-spark33	95.25% <91.91%> (-0.21%)	⬇️
2.12-root-spark34	95.48% <94.94%> (+0.02%)	⬆️
2.12-root-spark35	95.48% <94.94%> (+0.02%)	⬆️
2.13-root-spark35	96.04% <94.89%> (-0.02%)	⬇️

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