Asynchronous exceptions can put the external interpreter into an unrecoverable state

[Saizan]

Tracking relevant GHC issue https://gitlab.haskell.org/ghc/ghc/-/work_items/18852

If the host received an async exception while waiting for an external interpreter reply it will try to terminate the interpreter.

Ben's summary from the ticket:

As far as I can tell, there are three orthogonal issues here:

1. GHC is too aggressive in tearing down iserv when an exception is seen. Asynchronous exceptions cancelling computation are not a critical failure and shouldn't be treated as such.
2. If iserv does somehow fail then we don't correctly revert the iserv state to IservPending.
3. Even if (2) were fixed, we also fail to purge the linker state on failure.

We should fix all three of these.