Add new oracle-ee-cdb engine to the valid db engine on rds validator

[rodolfo-nadai-encora]

Hopefully this is fine, but feel free to ask any changes need it! PLEASE!

This is adding a new engine to be available in the RDS validator.

Closes

• Add RDS engine type "oracle-ee-cdb" #2333

[markpeek]

Thank you for the PR. I'd like to see a couple of changes outside of your change to this validator. Let me know if you want to do it or have me take it on.

1. Reorder the list alphabetically to better match up with the Valid Values listed here
2. Add any other missing values.
3. Figure out what to do with ones not listed in the documentation. I'd probably say just list them at the bottom and I can purge them sometime in the future.
4. Convert it from a tuple to a dict...the performance likely doesn't matter but hey, why not save some cycles?
5. And then ensure "make fix lint test" is successful with the changes.

[rodolfo-nadai-encora]

Yeah... NP, will do!

[rdenadai]

Please close this in favor of #2335

[markpeek]

Closed per author