Implement Smithy RPC v2 CBOR protocol

[david-perez]

Smithy RPC v2 CBOR protocol is a new protocol that has been added to Smithy 1.47 (release notes). This issue tracks all subtasks needed to add support for the protocol in smithy-rs.

• Upgrade Smithy to 1.47 #3552
• Add client support for RPC v2 CBOR protocol #3709
• Implement server-side support (Add server RPC v2 CBOR support #2544)
• Event streams #3772
• We need more and better tests to be confident in our implementation! Lack of coverage in RPC v2 CBOR protocol test suite smithy#2325

Paper cuts:

• Encode structures with all non-Optional member shapes using fixed-length CBOR maps #3745

[aajtodd]

Can we consider this done and close it?