lint: Call lint_scripted_diff from test_runner

Allowing to call the check from the test_runner allows for consistent
error messages and better UX by having a single test_runner for all
checks.

This requires the env var to be set for now. The next commit makes the
commit range optional.

ci/lint/06_script.sh

@@ -25,7 +25,6 @@ export COMMIT_RANGE
 echo
 git log --no-merges --oneline "$COMMIT_RANGE"
 echo
-test/lint/commit-script-check.sh "$COMMIT_RANGE"
 RUST_BACKTRACE=1 "${LINT_RUNNER_PATH}/test_runner"
 
 if [ "$CIRRUS_REPO_FULL_NAME" = "bitcoin/bitcoin" ] && [ "$CIRRUS_PR" = "" ] ; then