Retrie: automatically add imports when unfolding

[pepeiborra]

There are several TODOs for this:

haskell-language-server/src/Ide/Plugin/Retrie.hs

Line 243 in ba46353

-- TODO add imports to the rewrite

haskell-language-server/src/Ide/Plugin/Retrie.hs

Line 264 in ba46353

-- TODO add imports to the rewrite

haskell-language-server/src/Ide/Plugin/Retrie.hs

Line 391 in ba46353

-- TODO add the imports to the resulting edits