refactor: PKcols in table, ViewKeyDependency type

* Get PKcols inside tables - done with SQL for tables and
  with an additional step in Haskell for views.

  This fixes an fk column being considered as a pk column on views
  and corrects the test added on
  https://github.com/PostgREST/postgrest/pull/1875/files/1d549768580310e18aac4ffa6dbd01c5b77934a7#r853674126

* classify view key dependencies in SQL

* remove Column from Relationship

* Merge cols/fcols in Relationship and
  ensure allM2ORels and allViewsKeyDependencies fk columns
  are ordered - done by attnum in SQL

* Cardinality now contains relColumns instead of Relationship -
  this simplifies getJoinConditions.

src/PostgREST/Query/QueryBuilder.hs

@@ -53,7 +53,7 @@ getJoinsSelects :: ReadRequest -> ([SQL.Snippet], [SQL.Snippet]) -> ([SQL.Snippe
 getJoinsSelects rr@(Node (_, (name, Just Relationship{relCardinality=card,relTable=QualifiedIdentifier{qiName=table}}, alias, _, joinType, _)) _) (joins,selects) =
   let subquery = readRequestToQuery rr in
   case card of
-    M2O _ ->
+    M2O _ _ ->
       let aliasOrName = fromMaybe name alias
           localTableName = pgFmtIdent $ table <> "_" <> aliasOrName
           sel = SQL.sql ("row_to_json(" <> localTableName <> ".*) AS " <> pgFmtIdent aliasOrName)