Create naming_local_changes table in Rust naming table builder

Create naming_local_changes table in Rust naming table builder

Summary:
hh_server and hh_single_type_check will read the single value from this table when loading a saved state. It contains the naming table delta from a previously-loaded saved state, as an OCaml-marshaled blob. Since we are building the table from scratch in the naming table builder (and our Rust never attempts to save a naming table with a delta), the delta will always be empty. Create the table and write an empty delta upon creation.

The local changes table also contains a BASE_CONTENT_VERSION column. This column needs only be unique, as per this comment from [naming_table.ml](https://www.internalfb.com/code/fbsource/[a9b2544fea81]/fbcode/hphp/hack/src/naming/naming_table.ml?lines=406):

```
    (* Ideally, we would have a commit hash, which would result in the same
       content version given the same version of source files. However,
       using a unique version every time we save the naming table from scratch
       is good enough to enable us to check that the local changes diff
       provided as an argument to load_from_sqlite_with_changes_since_baseline
       is compatible with the underlying SQLite table. *)
```

Reviewed By: shayne-fletcher

Differential Revision: D40479834

fbshipit-source-id: 7f6cac170d4503ae5be3958e261c58e3e393206d