Ensure #second (and others) acts like #first AR finder

This PR addresses issue #13743 where the ordinal ActiveSupport Array extentions were not assuming a default order like first was.

As suggested by @dhh this commit bring the famous ordinal Array instance methods defined
in ActiveSupport into ActiveRecord as fully-fledged finders.

These finders ensure a default ascending order of the table's primary
key, and utilize the OFFSET SQL verb to locate the user's desired
record. If an offset is defined in the query, calling #second adds
to the offset to get the actual desired record.

Example:

        User.all.second

        # Before
        # => 'SELECT  "users".* FROM "users"'

        # After
        # => SELECT  "users".* FROM "users"   ORDER BY "users"."id" ASC LIMIT 1 OFFSET 1'

        User.offset(3).second

        # Before
        # => 'SELECT  "users".* FROM "users"'

        # After
        # => SELECT  "users".* FROM "users"   ORDER BY "users"."id" ASC LIMIT 1 OFFSET 4'