Ensure #second acts like #first AR finder
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.

Fixes #13743.
Merge pull request #13757 from terracatta/master

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

This variable is internal and should not be exposed to end users