Avocado should ignore readme validation for CADL data plane specs

[ruowan]

Feature requests from Ray.

What I meant is avocado validation will ignore swagger validation in CADL DPG scenario

Example PR: https://github.com/Azure/azure-rest-api-specs-pr/pull/10336/checks?check_run_id=10227564629

[raych1]

In CADL DPG scenario, avocado should ignore swagger validation as it doesn't have readme.md.

[raych1]

Discussed with @live1206 and SDK team Crystal, docs generation wouldn't depend on readme.md. @tianxchen-ms , please go ahead with this request change.

[leniatgh]

Unified pipeline precheck should not trigger Avocado in DPG scenario

[konrad-jamrozik]

Assigning myself as the new primary owner of Avocado and Unified pipeline.

[konrad-jamrozik]

As discussed by me with @ruowan possibly to be solved by:

• https://github.com/Azure/azure-rest-api-specs-pipeline/issues/68