Enable -fexpose-all-unfoldings

[sjakobi]

This allows us to reliably expose unfoldings for all exposed functions, instead of only those that are marked INLINABLE.

Also remove -fwarn-tabs which is enabled by default now.

[sjakobi]

I will finish this after merging #355.

[treeowl]

This will definitely do something. Let's make sure it's something good.

[sjakobi]

Apparently -fexpose-all-unfoldings does something very different than marking everything INLINEABLE:

https://gitlab.haskell.org/ghc/ghc/-/issues/21715#note_437347

I probably won't work on this further until I have a better understanding of the implications.

[doyougnu]

I also wasn't aware of this difference. I've made a note of it for the handbook.

I don't think -fexpose-all-unfoldings will do a better job than marking the exported functions with INILNEABLE. I would expect INLINEABLE to be better because GHC will have more information at the call site in whichever package is using u-c, and so it has more opportunity to optimize better.