[e-acsl:prepare_ast] replace the copy visitor by an in-place visitor

src/plugins/e-acsl/src/analyses/typing.ml

src/plugins/e-acsl/src/analyses/typing.mli

src/plugins/e-acsl/src/main.ml

src/plugins/e-acsl/src/project_initializer/prepare_ast.ml

src/plugins/e-acsl/src/project_initializer/prepare_ast.mli

src/plugins/e-acsl/tests/memory/vla.c