Haskell-language-server: Suggest new open imports

[expipiplus1]

It would be nice if in addition to closed (or qualified) imports HLS would suggest adding an open import for a missing symbol.

As far as I can tell this is the only bit which would need to change: https://github.com/jneira/ghcide/blob/f4f575dbdd0cf37fc60d2a11215cb35368d3a334/src/Development/IDE/Plugin/CodeAction.hs#L749-L767

Indiscriminate open imports are certainly not a good thing, but here and there they can be useful.

I'm pretty sure HIE used to suggest these.

[expipiplus1]

Ah, I realize that this should probably have been opened against ghcide

[konn]

+1 for it, since one can now make import list closed afterwards with the newly added import lense feature.

It is more desirable if it could automatically generate the hiding clause if there are some symbol collisions with already imported ones.

[expipiplus1]

@pepeiborra got there first: https://github.com/digital-asset/ghcide/pull/740