ContainerRegistry data-plane swagger improvement opportunities

1. From the offline conversations, [oauth2/token](https://learn.microsoft.com/en-us/rest/api/containerregistry/access-tokens/get-from-login?tabs=HTTP) usage is discouraged. Should the API be deprecated in future versions?
2. [ContainerRegistryBlob_DeleteBlob](https://github.com/Azure/azure-rest-api-specs/blob/c8d9a26a2857828e095903efa72512cf3a76c15d/specification/containerregistry/data-plane/Azure.ContainerRegistry/stable/2021-07-01/containerregistry.json#L341-L354) should list 404 as valid response (so that generated code does not throw when blob does not exist)
3. [`securityDefinitions`](https://github.com/Azure/azure-rest-api-specs/blob/main/specification/containerregistry/data-plane/Azure.ContainerRegistry/stable/2021-07-01/containerregistry.json#L18) sections should be reviewed: does ACR support basic oauth or api-key? Perhaps it should describe ACR scoped AAD tokens like [here](https://github.com/Azure/autorest/blob/a5d2727e1548a2bd965fb6981fd33cd70268aa68/docs/generate/authentication.md?plain=1#LL55-L55C2)?

Start with specification/containerregistry/data-plane/Azure.ContainerRegistry/stable/2021-07-01/containerregistry.json, especially the oauth2/token operation, ContainerRegistryBlob_DeleteBlob response definitions, and securityDefinitions section linked in the issue. Compare those entries with the referenced authentication guidance and determine the intended updates for deprecation, the 404 response, and ACR token authentication. Done means the unresolved questions are decided and the API specification reflects those decisions.

Written by the indexing model from the issue text.