Add a Date decoder to the pg adapter to type cast dates

at the connection level

Fix rails#51448

Type cast columns of type `date` to ruby `Date` when running a raw
query through `ActiveRecord::Base.connection.select_all`.

activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb

@@ -1159,6 +1159,7 @@ def add_pg_decoders
             "bool" => PG::TextDecoder::Boolean,
             "timestamp" => PG::TextDecoder::TimestampUtc,
             "timestamptz" => PG::TextDecoder::TimestampWithTimeZone,
+            "date" => PG::TextDecoder::Date,
           }
 
           known_coder_types = coders_by_name.keys.map { |n| quote(n) }