Roadmap to compacting ModIface

[Matthew Pickering]

Hello all,

I have written down the remaining steps which need to be taken in
order to compact a ModIface, which we hope will be useful for
applications such as IDEs to reduce GC time.

https://gitlab.haskell.org/ghc/ghc/issues/17097#roadmap-to-compacting-a-modiface

If there is anyone who wishes to help with this project then please
ping me on IRC. So far this is joint work between myself and Daniel G.

The first step we need to take is to get 1675 merged which replaces
the type backing a FastString from a ByteString to a ShortByteString
(and hence from a pinned ByteArray to an unpinned ByteArray).

https://gitlab.haskell.org/ghc/ghc/-/merge_requests/1675

Cheers,

Matt