TCGC + consumers adoption

[timotheeguerin]

Part of #4831.

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

Adopt the new examples format in the consumers.

Scope

• TCGC parses examples.yaml and surfaces real example content (all language generators consume examples via TCGC, so TCGC must adopt the format).
• SDK test generation consumes resolved examples (via examples-resolve) to generate test cases.
• Join Swagger operations to examples via x-id rather than embedded $ref.

Depends on #4834 (resolve) and #4835 (x-id emission).