Extracted Discussion XBlock: DiscussionsConfiguration and Permission

[salman2013]

Description:

Discussion XBlock's visibility is manage with provider setting and permission is setting for thread and comments. In this ticket we need to look up how we can manage the provider and permission code in extracted discussion block.

PR: openedx/openedx-platform#37912

[salman2013]

In edx-platform discussion 's comment permission and discussion 's provider is managing with django models and which is difficult to manage in discussion block extraction.
Ref: Discussion permissions
https://github.com/openedx/edx-platform/blob/5b1951228efca6afe0a3f18837236bd797cfadf4/lms/djangoapps/discussion/django_comment_client/permissions.py#L20

https://github.com/openedx/edx-platform/blob/5b1951228efca6afe0a3f18837236bd797cfadf4/openedx/core/djangoapps/django_comment_common/models.py#L163

Ref: DiscussionProvider
https://github.com/openedx/edx-platform/blob/5b1951228efca6afe0a3f18837236bd797cfadf4/openedx/core/djangoapps/discussions/models.py#L408

https://github.com/openedx/edx-platform/blob/5b1951228efca6afe0a3f18837236bd797cfadf4/openedx/core/djangoapps/discussions/models.py#L37

I created a service DiscussionConfig with the required methods to get the permissions and provider settings, added the service in runtime so that it can be easily accessible in xblocks-contrib.

PR: openedx/openedx-platform#37912