[improve][test] Add integration tests for the Debezium Oracle source connector

## Current state

`debezium/oracle` has **zero tests** — the `DebeziumOracleSource` connector is not exercised at all in CI. Note also that `debezium-connector-oracle` does not bundle the Oracle JDBC driver (`ojdbc`), so runtime driver availability in the NAR should be verified as part of this work.

## Proposal

Add a Testcontainers-based integration test following the `debezium/mysql` pattern, using the `gvenzl/oracle-free` image. This is the heaviest of the Debezium variants: the container needs archive-log mode, supplemental logging, and a LogMiner-privileged user configured via init scripts (see the Debezium Oracle connector setup docs), and the image is large (~1.5 GB), so CI runtime impact should be evaluated.

_Part of an integration-test coverage sweep of all connector modules._

Start with the debezium/mysql integration-test pattern and the debezium/oracle module, then consult the Debezium Oracle connector setup docs for archive logging, supplemental logging, and the LogMiner user. Add a Testcontainers test using gvenzl/oracle-free, verify runtime availability of the Oracle JDBC driver in the NAR, and evaluate the CI impact of the large image. Done means the Oracle source connector is exercised successfully in CI.

Written by the indexing model from the issue text.