Make ghc-pkg discoverable from ghc executable

**Describe the bug**
Currently there is no robust way to locate the `ghc-pkg` executable corresponding to a particular compiler. For this reason, Cabal currently implements a variety of heuristics to do the same. However, these can end up failing, in particular when the executable name is version-suffixed.

@hasufell and I discussed this some months ago after a `ghc-up` user encountered this problem, which resulted in [GHC #18807](https://gitlab.haskell.org/ghc/ghc/-/issues/18807). To address this I proposed that `ghc --info` should report the path to the corresponding `ghc-pkg` executable. This solves the problem nicely since Cabal already must query `--info` when configuring a package.

I have put together a very straightforward GHC implementation as [!4214](https://gitlab.haskell.org/ghc/ghc/-/merge_requests/4214). I have also written a [quick patch](https://gitlab.haskell.org/ghc/ghc/-/snippets/2710) implementing the Cabal support.

My sense is that this is the right solution to the problem. However, I'm also happy to hear alternatives. If there are no objections, I will backport to 8.10.5, 9.0.2, and 9.2.1 such that future users won't encounter this issue in the future.