GHCi output is not machine readable

Even with GHCiD, GHCi responses are simply not machine parseable. There's no reliable grammar and there's no escape support. This is most obvious with the `:show bindings` GHCi builtin command with multi-line nested strings.

This is an upstream issue inherently, but is likely something we can provide a compelling need for and contribute the source code. A simple JSON reply (or some other format) seems easy enough to implement.

I would prefer not to ship with a custom version of GHC, so upstreaming such an effort is likely the only course of action here.

Start by examining the GHCiD interaction with GHCi and reproducing the multiline nested-string case for the `:show bindings` command. Review the upstream GHCi constraints described in the issue and determine what machine-readable response format and upstream contribution path would be acceptable; done means a defined approach with reliable parsing requirements and an agreed upstream direction.

Written by the indexing model from the issue text.