Add domain created_time value to DescribeDomainResponse

[fimanishi]

Is your feature request related to a problem? Please describe.
It would be helpful to identify unused domains by having their creation date as one of the data points.

Proposed Solution
We've recently added created_time to the schema. We can return that value from domains_by_name_v2 when calling the DescribeDomain endpoint.

[demirkayaender]

It would be great to add the updated_time in the response as well.

[ansidev]

@demirkayaender It seems that only the Cassandra schema is up-to-date. How about other DBs' schemas?

[demirkayaender]

Work for this is scheduled. We will update here once MySQL and PostgreSQL schemas are updated.