Remove the need for `hi-file-parser`

After an extended debugging session with @simonmichael it came to my attention that Stack directly parses GHC's interface files via the `hi-file-parser` library. This is an unfortunate state of affairs. Interface files are interface to GHC and consequently come with no particular stability guarantees.

To make everyone's life easier, it would be better if we can find another way to expose the information that you need from interface files. Can you describe what information Stack needs that isn't currently available from other means? Also note that we have an open GHC proposal, the [extended dependency information proposal](https://github.com/ghc-proposals/ghc-proposals/pull/245), which may be helpful. We would love to have feedback on this.

I have opened [GHC #17620](https://gitlab.haskell.org/ghc/ghc/issues/17620) to track the GHC side of this.