System.ClientModel-based clients: set message.BufferResponse via RequestOptions from convenience methods

[annelo-msft]

Once we close Azure/azure-sdk-for-net#43932 (which we plan to ship in System.ClientModel 1.1.0-beta.4), we will need to make sure that generated SCM-based clients don't set message.BufferResponse in request creation helper methods (like we do in DPG clients as shown here). This is because the call to message.Apply(options) will override any value previously set on the message. Instead, protocol methods will always buffer responses based on the value of RequestOptions.BufferResponse, and any convenience method that needs to turn off response buffering should create an instance of RequestOptions, set options.BufferResponse = false, and pass options to the protocol method when it is called.

Feel free to reach out to me if a code sample for this is needed, and please include me as a reviewer of the PR that implements this feature prior to merging. Many thanks!