feat(sms): add scm_run_id to scan-create interface (#306)

For SMS, we would like to be able to connect a particular Scan object to
the SCM (source control manager) run_id that it is associated with.
Details
[here](https://www.notion.so/semgrep/SMS-Supportability-1273009241a880579e9ae90928391a0e?pvs=4#1313009241a880d79d77eb0d6773ad56).

If we create the SCM run before the scan exists (desirable because there
are actually many steps between us receiving a webhook and a Scan object
getting created, leading to a significant time delay), then when we
create the Scan, we need to know what the SCM run id is in order to
connect it to the Scan and update it as the Scan progresses. This
interface change allows us to pass the SCM run from the CLI to the
backend.

Changes in `semgrep` to follow this PR will actually set this value
based on an environment variable and then send it to the app.

- [x] I ran `make setup && make` to update the generated code after
editing a `.atd` file (TODO: have a CI check)
- [x] I made sure we're still backward compatible with old versions of
the CLI.
For example, the Semgrep backend need to still be able to *consume* data
generated
	  by Semgrep 1.17.0.
See
https://atd.readthedocs.io/en/latest/atdgen-tutorial.html#smooth-protocol-upgrades

semgrep_output_v1.atd

@@ -1422,6 +1422,9 @@ type scan_metadata = {
   unique_id: uuid; (* client generated uuid for the scan *)
   requested_products: product list;
   ~dry_run: bool; (* from 1.47.0 *)
+  (* since 1.96.0 *)
+  (* unique id associated with the scan run in the source control manager (e.g. github or gitlab) *)
+  ?scm_run_id: string option;
 }
 
 (* Sent by the CLI to the POST /api/cli/scans to create a scan. *)