Handle TIMESTAMP WITH TIMEZONE separately from TIMEZONE

[yahonda]

Fixes #1206

rails/rails#27962 moves TypeCastingTest from sqlite3 specific one to generic then some tests are failing because type_cast and quote method both call quoted_date for Date and Time class objects in abstract adapter but Oracle enhanced adapter does not, using its own implementation.

This pull request lets generic Date and Type objects handled by abstract adapter implementation.
For non-generic data types including timezone ActiveRecord::OracleEnhanced::Type::TimestampTz type has been created and TimestampTz type is handled as it used to.

Oracle enhanced adapter now relies on Time::DATE_FORMATS defined in ActiveSupport by this change.
Therefore changing NLS_DATE_FORMAT and NLS_TIMESTAMP_FORMAT are not working and will not be supported.

[yahonda]

This pull request addresses these 4 failures:

 33) Failure:
FinderTest#test_hash_condition_utc_time_interpolation_with_default_timezone_local [/home/yahonda/git/rails/activerecord/test/cases/finder_test.rb:829]:
--- expected
+++ actual
@@ -1 +1 @@
-#<Topic id: 1, title: "The First Topic", author_name: "David", author_email_address: "david@loudthinking.com", written_on: "2003-07-16 14:28:11", bonus_time: "2005-01-30 14:28:00", last_read: "2004-04-15", content: "Have a nice day", important: nil, approved: false, replies_count: 1, unique_replies_count: 0, parent_id: nil, parent_title: nil, type: nil, group: nil, created_at: "2017-03-30 11:56:59", updated_at: "2017-03-30 11:56:59">
+nil


 42) Failure:
ActiveRecord::ConnectionAdapters::TypeCastingTest#test_type_cast_date [/home/yahonda/git/rails/activerecord/test/cases/quoting_test.rb:165]:
Expected: "2017-03-30"
  Actual: Thu, 30 Mar 2017


 43) Failure:
ActiveRecord::ConnectionAdapters::TypeCastingTest#test_type_cast_time [/home/yahonda/git/rails/activerecord/test/cases/quoting_test.rb:171]:
Expected: "2017-03-30 11:58:53.015137"
  Actual: 2017-03-30 11:58:53 UTC


 44) Failure:
ActiveRecord::ConnectionAdapters::QuoteARBaseTest#test_type_cast_ar_object [/home/yahonda/git/rails/activerecord/test/cases/quoting_test.rb:247]:
Expected: "2017-02-14 12:34:56.789000"
  Actual: 2017-02-14 12:34:56 UTC