RPC returning table alias now works for pg 11/12 (#2737)

The new LATERAL query used for calling the function, introduced on
https://github.com/PostgREST/postgrest/pull/2677, failed on functions
that returned a domain like `CREATE DOMAIN projects_domain AS projects`.

Work around that by changing the query conditionally, by
obtaining a bool that represents the composite alias on the SchemaCache
and only do this on pg 11 and 12.

src/PostgREST/Plan.hs

@@ -56,6 +56,7 @@ import PostgREST.SchemaCache.Identifiers  (FieldName,
                                            Schema)
 import PostgREST.SchemaCache.Proc         (ProcDescription (..),
                                            ProcParam (..), ProcsMap,
+                                           procReturnsCompositeAlias,
                                            procReturnsScalar,
                                            procReturnsSetOfScalar)
 import PostgREST.SchemaCache.Relationship (Cardinality (..),
@@ -550,6 +551,7 @@ callPlan proc ApiRequest{iPreferences=Preferences{..}} paramKeys args readReq =
 , funCArgs = Just args
 , funCScalar = procReturnsScalar proc
 , funCSetOfScalar = procReturnsSetOfScalar proc
+, funCRetCompositeAlias = procReturnsCompositeAlias proc
 , funCReturning = inferColsEmbedNeeds readReq []
 }
   where