feat: filter users by github user id in the users list CLI command (#17029)

Add the `--github-user-id` option to `coder users list`, which makes the
command only return users with a matching GitHub user id. This will
enable https://github.com/coder/start-workspace-action to find a Coder
user that corresponds to a GitHub user requesting to start a workspace.

coderd/database/queries/users.sql

@@ -223,6 +223,11 @@ WHERE
 			created_at >= @created_after
 		ELSE true
 	END
+	AND CASE
+		WHEN @github_com_user_id :: bigint != 0 THEN
+			github_com_user_id = @github_com_user_id
+		ELSE true
+	END
 	-- End of filters
 
 	-- Authorize Filter clause will be injected below in GetAuthorizedUsers