x-id emission: typespec-autorest + transitional JSON

[timotheeguerin]

Part of the Unified Examples Format epic.

RFC: https://github.com/Azure/azure-rest-api-specs/blob/rfc/unified-examples-format/documentation/rfc/unified-examples-format.md

Add x-id emission to @azure-tools/typespec-autorest.

Scope

• Emit an x-id extension (the full operation identity, $namespace + operation key) on every operation.
• Stop embedding x-ms-examples $ref blocks in generated Swagger.
• Transitional: optionally emit x-ms-examples JSON generated from the new format for consumers not yet migrated.
• Confirm the doc-team pipeline can consume x-id in place of the embedded $ref.