Import improvements from MTL 2.2 and 2.3

[marcin-serwin]

This MR brings the code up to date with the current version of MTL. Among others it introduces the Accum and Select monad classes, defines alternative minimal required implementations (e.g. state in StateMonad), and removes old reexports.

This MR is quite big, but each commit should be self contained and easy to cherry-pick if something is undesirable. The code is basically copied from MTL and adapted to use type families instead of dependencies. This means that some of the MTL breaking changes are also introduced so I've bumped the package version to 0.4.0.0.

Additionally, I've enabled the Safe Haskell extension everywhere so that the code can be imported to projects that also use it. MTL was using DerivingVia which is not considered Safe now, so I've rewritten those derivations by hand to avoid introducing Trustworthy modules.