Support the OpenID Provider Discovery Metadata

## Issue
I getting following issues while trying to support logout

*** Assertion failure in -[OIDEndSessionRequest endSessionRequestURL], OIDEndSessionRequest.m:184
2023-03-09 14:54:36.180270+0530 EnablePlus[22485:292112] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'The service configuration is missing an end_session_endpoint.'

Are there any plans to support the OpenID Provider Discovery Metadata for "ping_end_session_endpoint" instead of using "end_session_endpoint" since it is common for Ping Federate.
or is there anyway to override the "end_session_endpoint" to "ping_end_session_endpoint"

## Environment

* **Your Identity Provider**: `PingFederate`
* **Platform that you're experiencing the issue on**: `both`
* **Are you using Expo?** No

まず、OIDEndSessionRequest.m の assertion と、レポートに記載されているサービス設定を確認し、続いて両プラットフォームでの OpenID Provider Discovery Metadata の処理を追跡します。PingFederate の ping_end_session_endpoint がサポートされるか、または end_session_endpoint がない場合のエラーを発生させずに明示的に上書きできれば完了です。

索引モデルが issue の本文から書いたものです。