[Core] Remove pg resource notation from user-facing APIs.

[rkooo567]

Description

When pg is created, the existing resources are allocated, and we dynamically create custom formatted resources for scheduling. This is the "implementation detail" of the placement group. However, this formatted custom resources are exposed via several user facing APIs. E.g., Dashboard. ray.available_resources() (we may want to keep it for debugging purpose). state APIs. We removed this problem from ray status by parsing the placement group resources. We should do it for all the user-facing APIs.

Use case

No response