Fix #4951: Increase test stack size before bootstrap
Fix #4951: Increase test stack size before bootstrap

To test, use `testCompilation inductive-implicits-bench` before and after,
locally.

dotty-staging/dotty,som-snytt/dotty,lampepfl/dotty,som-snytt/dotty,sjrd/dotty,dotty-staging/dotty,som-snytt/dotty,dotty-staging/dotty,sjrd/dotty,lampepfl/dotty,sjrd/dotty,dotty-staging/dotty,som-snytt/dotty,lampepfl/dotty,sjrd/dotty,som-snytt/dotty,dotty-staging/dotty,lampepfl/dotty,lampepfl/dotty,sjrd/dotty