[Improve][Oracle-CDC] Remove duplicate load table names

[hailin0]

Purpose of this pull request

Does this PR introduce any user-facing change?

How was this patch tested?

Check list

• If any new Jar binary package adding in your PR, please add License Notice according
  New License Guide
• If necessary, please update the documentation to describe the new feature. https://github.com/apache/seatunnel/tree/dev/docs
• If you are contributing the connector code, please check that the following files are updated:
  1. Update plugin-mapping.properties and add new connector information in it
  2. Update the pom file of seatunnel-dist
  3. Add ci label in label-scope-conf
  4. Add e2e testcase in seatunnel-e2e
  5. Update connector plugin_config

[Copilot]

Pull Request Overview

This pull request refactors the Oracle dialect for the CDC connector to remove duplicate load table names. The changes replace a JDBC-based table listing approach with a stream over an existing tableMap key set.

• Removed the direct JDBC connection and OracleConnectionUtils.listTables() call.
• Introduced stream-based collection of TableId objects via tableMap.
• Removed the now unnecessary OracleConnectionUtils import.