Fix #2429: Replaced slow UNION query with optimized all_objects query

[LohithaNadimpalli]

Summary:

Replaced the slow UNION-based SQL query in connection.rb with a single query using all_objects to improve performance, as discussed in #2429.

Details:

• Reduced 4 UNION ALL queries into one optimized query using all_objects.
• Suggested by Oracle DBAs due to 2-second delay in production.
• I'm a beginner contributor and wasn’t able to run tests locally.
  Kindly review and let me know if further changes are needed.

Closes #2429

[LohithaNadimpalli]

Hi maintainers! I'm a beginner contributor and excited to make my first PR to this project. Please let me know if anything needs improvement. 🙏

[matthewtusker]

We've done some more research into this and found a DBMS_UTILITY.NAME_RESOLVE function in Oracle which resolves names, and supports db links. It's much faster than the existing SQL, and faster than the all_objects query. I think you should look into that if you're looking to make a contribution to Oracle Enhanced.