Fix ApacheHttpClient Proxy Preemptive Auth Failure

[S-Saranya1]

Fix ApacheHttpClient proxy authentication failure issue with preemptive authentication.

Motivation and Context

Users configuring proxy preemptive authentication with preemptiveBasicAuthenticationEnabled set to true were experiencing 407 error which was not expected.

Fixes #5884

Modifications

Added synthetic challenge processing in addPreemptiveAuthenticationProxy() method to initialize BasicScheme for preemptive authentication

Testing

Added unit test to verify preemptive authentication functionality

Screenshots (if appropriate)

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)

Checklist

• I have read the CONTRIBUTING document
• Local run of mvn install succeeds
• My code follows the code style of this project
• My change requires a change to the Javadoc documentation
• I have updated the Javadoc documentation accordingly
• I have added tests to cover my changes
• All new and existing tests passed
• I have added a changelog entry. Adding a new entry must be accomplished by running the scripts/new-change script and following the instructions. Commit the new file created by the script in .changes/next-release with your changes.
• My change is to implement 1.11 parity feature and I have updated LaunchChangelog

License

• I confirm that this pull request can be released under the Apache 2 license

[sonarqubecloud]

Quality Gate failed

Failed conditions
62.5% Coverage on New Code (required ≥ 80%)

See analysis details on SonarQube Cloud

[github-actions]

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