Finalize v5.0 (part1)

[aslesarenko]

• implemented some // TODO optimize
• more tests for TypeSerializer
• negative test cases when lambda is not with single argument
• more // TODO cover
• fixed CollectionUtil.joinSeq method + tests
• identified the problem with Coll.append (added regression tests for ET v0, v1)

[codecov]

Codecov Report

Merging #761 (5abc74e) into v5.0-finalize (0fa0448) will increase coverage by 0.10%.
The diff coverage is 85.00%.

@@                Coverage Diff                @@
##           v5.0-finalize     #761      +/-   ##
=================================================
+ Coverage          71.53%   71.64%   +0.10%     
=================================================
  Files                246      246              
  Lines              18731    18724       -7     
  Branches             603      624      +21     
=================================================
+ Hits               13400    13414      +14     
+ Misses              5331     5310      -21     

Impacted Files	Coverage Δ
core/src/main/scala/scalan/TypeDescs.scala	83.33% <ø> (ø)
...ain/scala/special/collection/CollsOverArrays.scala	86.48% <ø> (ø)
.../main/scala/special/sigma/SigmaDslOverArrays.scala	45.16% <ø> (ø)
.../main/scala/org/ergoplatform/ErgoLikeContext.scala	90.09% <ø> (ø)
...n/scala/org/ergoplatform/ErgoLikeInterpreter.scala	90.00% <ø> (ø)
.../src/main/scala/sigmastate/DataValueComparer.scala	94.41% <ø> (ø)
...state/src/main/scala/sigmastate/UnprovenTree.scala	100.00% <ø> (ø)
...ain/scala/sigmastate/eval/CostingDataContext.scala	78.62% <ø> (ø)
...rc/main/scala/sigmastate/eval/RuntimeCosting.scala	91.05% <ø> (ø)
...ala/sigmastate/interpreter/ErgoTreeEvaluator.scala	93.93% <ø> (+2.08%)	⬆️
... and 21 more

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[kushti]

Finally, LGTM, but please check PR description (outdated now)