chore(mcp): update interfaces for mcp metabase scan metrics (#414)

- [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 1.50.0.
See
https://atd.readthedocs.io/en/latest/atdgen-tutorial.html#smooth-protocol-upgrades
Note that the types related to the semgrep-core JSON output or the
semgrep-core RPC do not need to be backward compatible!
- [ ] Any accompanying changes in `semgrep-proprietary` are approved and
ready to merge once this PR is merged

PR in `semgrep-proprietary`​:
semgrep/semgrep-proprietary#4823

Author: liukatkat

semgrep_output_v1.atd

@@ -1154,6 +1154,11 @@ type prefiltering_stats <ocaml attr="deriving show"> = {
 (* Final 'semgrep scan' output  *)
 (*****************************************************************************)
 
+type mcp_scan_results = {
+  rules: string list;
+  total_bytes_scanned: int;
+}
+
 (* TODO: rename to scan_output at some point *)
 type cli_output = {
     (* since: 0.92 *)
@@ -1203,6 +1208,9 @@ type cli_output_extra = {
      * logged in.
      * EXPERIMENTAL: since: 1.125.0 *)
     ?subprojects: cli_output_subproject_info list option;
+
+    (* MCP scan results. *)
+    ?mcp_scan_results: mcp_scan_results option;
 }
 
 (*****************************************************************************)