Fix withOracle and holes semantics, do not treat them as special trees

Game.scala

library/annotation/package.scala

library/lang/synthesis/package.scala

src/main/scala/leon/codegen/CodeGeneration.scala

src/main/scala/leon/frontends/scalac/ASTExtractors.scala

src/main/scala/leon/frontends/scalac/CodeExtraction.scala

src/main/scala/leon/purescala/PrettyPrinter.scala

src/main/scala/leon/purescala/ScalaPrinter.scala

src/main/scala/leon/purescala/TreeOps.scala

src/main/scala/leon/purescala/Trees.scala

src/main/scala/leon/solvers/z3/AbstractZ3Solver.scala

src/main/scala/leon/synthesis/ChooseInfo.scala

src/main/scala/leon/synthesis/ConvertWithOracles.scala

src/main/scala/leon/synthesis/CostModel.scala

src/main/scala/leon/synthesis/Rules.scala

src/main/scala/leon/synthesis/Solution.scala

src/main/scala/leon/synthesis/SynthesisOptions.scala

src/main/scala/leon/synthesis/SynthesisPhase.scala

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

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