Split out cron and non-cron unit evals (#42472)

Release Notes:

- N/A

---------

Co-authored-by: Bennet Bo Fenner <bennetbo@gmx.de>

script/run-unit-evals

@@ -2,4 +2,8 @@
 
 set -euxo pipefail
 
+if [ -n "${UNIT_EVAL_COMMIT:-}" ]; then
+  git checkout "$UNIT_EVAL_COMMIT"
+fi
+
 GPUI_TEST_TIMEOUT=1500 cargo nextest run --workspace --no-fail-fast --features unit-eval --no-capture -E 'test(::eval_)'