Extend Package to include id

This commit
1. rename Package with PackageBaseName
2. Pacakge = (PackageBaseName, Maybe String) to save its id
3. Expose packages with id if available

Language/Haskell/GhcMod/Gap.hs

@@ -234,8 +234,10 @@ addDevPkgs df pkgs = df''
     df' = dopt_set df Opt_HideAllPackages
 #endif
     df'' = df' {
-        packageFlags = map ExposePackage pkgs ++ packageFlags df
+        packageFlags = map expose pkgs ++ packageFlags df
       }
+    expose (pkg, Nothing) = ExposePackage pkg
+    expose (_, Just pid) = ExposePackageId pid
 
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