Improve questions for process load/reload

I set `haskell-process-load-or-reload-prompt` to `t`, so every time I start Haskell process I need to answer questions. Can you fix two things:
1. When I abort the “dialog” at some point (via `keyboard-quit`) it should not create new empty buffer, preferably, nothing should happen at all.
2. Consider removing question about Cabal directory. This package can find Cabal files pretty well, I cannot imagine situation when anyone would want to set different Cabal directory than that that is found automatically.

Start at the implementation of `haskell-process-load-or-reload-prompt` and reproduce process startup with it set to `t`, interrupting the dialog with `keyboard-quit`. Done means aborting creates no new empty buffer and the questions no longer ask for a Cabal directory.

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