Remove MutableTyped from Identifiers and eliminate it completely

src/main/scala/leon/datagen/VanuatooDataGen.scala

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

src/main/scala/leon/purescala/Common.scala

...in/scala/leon/purescala/CompleteAbstractDefinitions.scala

src/main/scala/leon/purescala/Constructors.scala

src/main/scala/leon/purescala/Definitions.scala

src/main/scala/leon/purescala/FunctionClosure.scala

src/main/scala/leon/purescala/MethodLifting.scala

src/main/scala/leon/purescala/ScopeSimplifier.scala

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

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

src/main/scala/leon/purescala/TypeTreeOps.scala

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

src/main/scala/leon/repair/rules/GuidedDecomp.scala

src/main/scala/leon/solvers/smtlib/SMTLIBCVC4Target.scala

src/main/scala/leon/solvers/smtlib/SMTLIBTarget.scala

...main/scala/leon/solvers/templates/TemplateGenerator.scala

src/main/scala/leon/solvers/templates/Templates.scala

src/main/scala/leon/solvers/templates/UnrollingBank.scala

src/main/scala/leon/synthesis/ConvertHoles.scala