Wrapping up the immediate changes for #[derive(WpDerivedRequest)]

[oguzkocer]

This PR wraps up the immediate work related to #[derive(WpDerivedRequest)] and includes miscellaneous changes:

• Removes the 2 suffix from request builder types we temporarily used during the transition.
• Simplifies the RequestBuilder type to remove request execution and renames it as InnerRequestBuilder to make it easier to separate from the generated types such as UsersRequestBuilder.
• Cleans up the config type used in WpDerivedRequest to make it easier to work with.
• The request executor will now build its own request builder. Prior to this change, we had to build a UsersRequestBuilder to pass it into UsersRequestExecutor's constructor, but now we pass the arguments required to build UsersRequestBuilder instead.
• The generated request builder & executor now accepts a WpAuthentication instead of InnerRequestBuilder and builds the inner type itself. This comes at a tiny additional memory cost, however it improves the function signature and some of the extra restrictions.
• Makes generated request builder & executor available to pub

[jkmassel]

Reviewed in sync call – this is mostly just cleanup and renaming things (and removing some code)