Update the /identity-providers/ API to manage user-defined federated authenticators.

[Thisara-Welmilla]

Issue:

• Provide API for the new custom authentication management product-is#21216

This PR introduces improvements to the following APIs for managing user-defined federated authenticators:

• /identity-providers: Updated the request body for the PUT request to accept both authenticator configuration models.
• /identity-providers/{identity-provider-id}/federated-authenticators: Updated the request body for the PUT request to accept both authenticator configuration models.
• /identity-providers/{identity-provider-id}/federated-authenticators/{federated-authenticator-id}: Updated the response and request bodies for both GET and PUT requests to accommodate both models.

Service layer PR:

• Add support for managing custom federated authenticators. carbon-identity-framework#6105