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