Introduce `Distribution.Client.Compat.Prelude`

This is supposed to become more or less a superset of Cabal's
`Distribution.Compat.Prelude`.

As a side-effect,t his exposes `Distribution.Compat.Prelude` from the
Cabal library (which may be actually a good thing, as it may be useful
module to Setup.hs writers).

Cabal/Cabal.cabal

@@ -315,6 +315,7 @@ library
     Distribution.Compat.Exception
     Distribution.Compat.Graph
     Distribution.Compat.Internal.TempFile
+    Distribution.Compat.Prelude
     Distribution.Compat.ReadP
     Distribution.Compat.Semigroup
     Distribution.Compat.Stack
@@ -415,7 +416,6 @@ library
     Distribution.Compat.Binary
 
   other-modules:
-    Distribution.Compat.Prelude
     Distribution.Compat.CopyFile
     Distribution.Compat.GetShortPathName
     Distribution.Compat.MonadFail

cabal-install/Distribution/Client/Compat/Prelude.hs

+-- | This module does two things:
+--
+-- * Acts as a compatiblity layer, like @base-compat@.
+--
+-- * Provides commonly used imports.
+--
+-- This module is a superset of "Distribution.Compat.Prelude" (which
+-- this module re-exports)
+--
+module Distribution.Client.Compat.Prelude
+  ( module Distribution.Compat.Prelude
+  , Prelude.IO
+  ) where
+
+import Prelude (IO)
+import Distribution.Compat.Prelude hiding (IO)

cabal-install/cabal-install.cabal

@@ -311,6 +311,7 @@ executable cabal
         Distribution.Client.Win32SelfUpgrade
         Distribution.Client.Compat.ExecutablePath
         Distribution.Client.Compat.FilePerms
+        Distribution.Client.Compat.Prelude
         Distribution.Client.Compat.Process
         Distribution.Client.Compat.Semaphore
         Distribution.Solver.Types.ComponentDeps