feat(aws): implement phase 1F 100% service fleet activation with CBOR support

[skyoo2003]

Summary

Phase 1F completes 100% service fleet serving activation across DevCloud by implementing native RFC 8949 CBOR encoding and decoding and wiring Smithy rpcv2Cbor protocol support.

With this change, every single one of the 431 registered AWS services in DevCloud now serves at least one real operation (431 of 431, 100.0%). Zero registered-only services remain in the fleet.

Key Improvements

1. Lightweight Native CBOR Engine (internal/shared/cbor):
   • Implemented standard-library-only RFC 8949 CBOR encoder and decoder.
   • Supports seamless JSON $\leftrightarrow$ CBOR translation (JSONToCBOR, CBORToJSON) for numbers, strings, maps, slices, primitives, and nulls.
2. Smithy rpcv2Cbor Protocol Support:
   • Added smithy.protocols#rpcv2Cbor detection in internal/codegen/parser.go ("rpcv2-cbor").
   • Admitted rpcv2-cbor into generic CRUD engine classification and runtime handling (engineServable & crud.Servable).
   • Added RPC-v2 routing in gateway: detects smithy-protocol: rpc-v2-cbor, application/cbor Content-Type, and /service/{Service}/operation/{Op} path pattern.
   • Normalizes and routes partnercentral SigV4 scope and /service/PartnerCentralRevenueMeasurement/... to partnercentralrevenuemeasurement.
   • Transcodes inbound CBOR request bodies to JSON for the engine, and outbound responses to CBOR with smithy-protocol: rpc-v2-cbor headers.
3. Fidelity & Fleet Serving Milestones:
   • 431 of 431 registered AWS services serving $\ge$ 1 operation (100.0%)!
   • Registered-only services reduced from 1 $\rightarrow$ 0.
   • Compatibility-tested services increased from 426 $\rightarrow$ 427 (partnercentralrevenuemeasurement removed from boto3 exclusions and smoke-tested).
   • Promoted all 18 partnercentralrevenuemeasurement operations into auto-crud.
   • All tests passing cleanly: 615 passed compatibility suite, full go test ./... suite clean.