Fix WPGraphQL support for extended post types and taxonomies

[pdclark]

Summary

• Adds WPGraphQL fallback in setup_content_types() for extended post types and taxonomies, matching the existing REST API pattern.
• When a third-party plugin registers a CPT before Pods' register_post_type_args filter is in place, show_in_graphql is now set directly on the global post type/taxonomy object.

Fixes #7450

Test plan

• Extend a third-party CPT registered with public => false as a Pod
• Enable WPGraphQL in the Pod settings
• Verify the CPT appears in WPGraphQL without needing a manual filter workaround
• Verify existing WPGraphQL integration for Pods-created CPTs still works

[what-the-diff]

PR Summary

• Upgrade in the GraphQL logic for post types
  The update includes a new functionality that enables GraphQL representation for pre-existing post types. This is an adjustment that takes into account the possibility of post types being registered prior to the initiation of the register_post_type_args filter.

• Added checks for wpgraphql_enabled setting
  Before feeding GraphQL information into the system, the PR has added a check to ascertain if the wpgraphql_enabled setting is active.

• Error handling enhancements
  Errors and exceptions that may occur during the process are now effectively dealt with. Using a try-catch block, any errors can be logged for further troubleshooting and rectification.

• Mapping of GraphQL names for post types
  There's a new feature mapping GraphQL single and plural names corresponding to existing post types. This allows more organized and logical presentation in the GraphQL framework.

• Support for existing taxonomies in GraphQL
  Similar to post types, this update also offers support for GraphQL representation of existing taxonomies which were possibly registered before the initiation of register_taxonomy_args filter. The process follows similar checks and error handling as in the post type enhancements.