[feature request] Fill in position info for JavaSootMethod

[Liyw979]

https://github.com/soot-oss/SootUp/blob/917133e974c6c377d573dfbb291c299838a40551/sootup.java.bytecode/src/main/java/sootup/java/bytecode/frontend/AsmClassSource.java#L140-L146

[swissiety]

recipe: calculate min and max Position in the Stmts (maybe be the first and last Stmt but not necessarily!) and create a new Position with that info for line :146