Stack stress test - iterated execution to expose rare bugs

In https://github.com/commercialhaskell/stack/issues/2106, the idea of stress testing stack on different platforms is brought up. This makes sense to me.

Start by reading issue 2106, which contains the referenced discussion about stress testing Stack across platforms. Clarify the testing scope, execution loop, supported platforms, and success criteria before identifying implementation and test entry points; done means a reproducible stress test that can expose rare bugs across the agreed platforms.

Written by the indexing model from the issue text.