Azure.Core 2.0: Update Response, Response<T>, and NullableResponse<T>

[annelo-msft]

Description

Many of the basic Azure.Core types now have analogous types in the System.ClientModel library. In order to follow the DRY engineering principle, we plan to update Azure.Core to reuse functionality from these types, using either inheritance or adapters in most cases.

This PR makes the following changes:

• Azure.Core Response inherits from System.ClientModel PipelineResponse
• Azure.Core NullableResponse<T> inherits from System.ClientModel ClientResult<T?>

Design Motivation

Despite some complexity in the implementation of the inheritance of Response from PipelineResponse, this is required in order to be able to write a single pipeline policy that will work in both Azure.Core and System.ClientModel pipelines.

Context

This PR is a smaller chunk of #41773 to make it easier to review. In addition, it this PR targets the feature/azure.core-2.0 feature branch because we cannot move the Azure.Core 2.0 integration into main until after System.ClientModel 1.1.0 is GA.

[azure-sdk]

API change check

API changes are not detected in this pull request.

[annelo-msft]

Discussed offline that this is OK to merge - we may revisit the internal DefaultResponse class if there is another way to address the need of ClientResult to get a non-null Response from the NullableResponse<T> default constructor.