Replace `freer-simple` and `freer-extras` by `polysemy`

`freer-simple` is no longer maintained and does not compile with GHC 9.12.

A more stable effect system should be used instead, typically `polysemy`.
Ideally, this should replace usage of `freer-simple`, but also the ad-hoc helpers living in `freer-extras.`
If freer-extras is not totally super-seeded by `polysemy`, this should be documented under this issue, and ad-hoc fixes should be found based on each missing use case.