[GenAI] Fix 11755: Providing a sensible default implementation in the base class that returns a new ConnectionPoolConfiguration instance

[Jarvx]

Issue: #11755

Bug description

TwitterHttpClientConfiguration does not compile because getConnectionPoolConfiguration() must be implemented.

Root cause & Fix

The issue is that HttpClientConfiguration.getConnectionPoolConfiguration() is declared abstract, forcing subclasses (like user examples) to implement it. To fix this without changing the behavior of existing concrete classes, we can provide a sensible default implementation in the base class that returns a new ConnectionPoolConfiguration instance. Subclasses that already override the method (e.g. DefaultHttpClientConfiguration, ServiceHttpClientConfiguration) will continue to work unchanged. This is a minimal, backward-compatible change.

Steps to reproduce

Please use this command to see the test result:

./gradlew :test-suite-kotlin-ksp:test