Refactor test generation/extraction

src/main/scala/leon/repair/Repairman.scala

src/main/scala/leon/synthesis/ExamplesFinder.scala

src/main/scala/leon/synthesis/InOutExample.scala

src/main/scala/leon/synthesis/Problem.scala

src/main/scala/leon/synthesis/rules/BottomUpTegis.scala

src/main/scala/leon/synthesis/rules/CegisLike.scala

src/main/scala/leon/synthesis/rules/TegisLike.scala