add a function in utils to convert a def path(String) into its def id
the code refers to that of clippy
fix bugs in graph building
the former version view a Place as a local, while more than one assignments can take place on a Place, thus we should identify them. this pr supports a part of variants of Place, and add virtual node markers in the graph
correspondingly implement to_dot_graph functions
refactor the code to extact the debug code together
utilsto convert a def path(String) into its def idPlaceas a local, while more than one assignments can take place on aPlace, thus we should identify them. this pr supports a part of variants ofPlace, and add virtual node markers in the graphto_dot_graphfunctions