Ensure eval plugin Print class doesn't rely on Prelude being in scope

[akrmn]

Hi,

This PR is pretty much what it says on the tin :)

The reason I need this is because the codebase at work uses {-# NoImplicitPrelude #-}, together with a custom prelude that includes show :: Show a => a -> Text, which doesn't play well with the Eval plugin. Currently, we get errors like:

Request workspace/executeCommand failed.
  Message: Couldn't match type ‘Text’ with ‘[Char]’
Expected type: IO String
  Actual type: IO Text

  Code: -32603 

This is because the Print class, as defined on Ide.Plugin.Eval.Code, uses whatever show is in scope. Having a qualified Prelude in scope when Print is defined should be enough to avoid that, and I can't think of any drawbacks.

Thanks for your consideration and for all the great work on HLS so far!

[pepeiborra]

Thank you señor Ackermann! And best wishes