Remove CIBA push auth related classes and configs

[Akila94]

Remove CIBA push auth related classes and configs

This PR removes CIBA related classes and configs from the repository since these will be removed in the future when moving to the newly implemented CIBA in Identity Server.

Issue link: #233

Doc Issue: wso2/docs-open-banking#908

Applicable Labels: CIBA, OB3

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Development Checklist

1. Build complete solution with pull request in place.
2. Ran checkstyle plugin with pull request in place.
3. Ran Findbugs plugin with pull request in place.
4. Ran FindSecurityBugs plugin and verified report.
5. Formatted code according to WSO2 code style.
6. Have you verified the PR doesn't commit any keys, passwords, tokens, usernames, or other secrets?
7. Migration scripts written (if applicable).
8. Have you followed secure coding standards in WSO2 Secure Engineering Guidelines?

Testing Checklist

1. Written unit tests.
2. Verified tests in multiple database environments (if applicable).
3. Tested with BI enabled (if applicable).