source-oracle: support CDB databases

[mdibaiee]

Description:

• Support CDB databases. It is simpler than I thought, basically either the user connects directly to a root container database (unlikely), or they connect to a pluggable database (PDB). What we need to do is essentially switching the session to the CDB when running logminer, since logminer cannot run on PDBs.
• I tested this by creating a container database in Oracle Cloud and running one of our tests against it. I have updated the tests of the connector so that they are run both against a non-container database and a container one. I have not run the full test suite yet... some connectivity issues from my machine are making it difficult... I'll see if I can do it
• Docs pull-request to go with this: docs: OracleDB container database setup flow#1843

Workflow steps:

(How does one use this feature, and how has it changed)

Documentation links affected:

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Notes for reviewers:

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