mocks for creating CFG's from adjacency lists

`type t``= int```
`type id``= int```
`val hash : 'a ‑> int`
`val id : 'a ‑> 'a`
`val loc : 'a ‑> 'b`
`val underlying_node : 'a ‑> 'b`
`val of_underlying_node : 'a ‑> 'b`
`val kind : 'a ‑> InferIR.Procdesc.Node.nodekind`
`val compare_id : InferStdlib.IStd.Int.t ‑> InferStdlib.IStd.Int.t ‑> int`
`val pp_id : F.formatter ‑> int ‑> unit`
`module OrderedId : sig ... end`
`module IdMap : sig ... end`
`module IdSet : sig ... end`