pipelines: Deprecate old pipelines

[bwateratmsft]

(title)

Should give notification to:

• Logic Apps
• CosmosDB
• VMs?
• API Management
• GHCP4Az
• Azure Load Testing
• Entra extension

[bwateratmsft]

We should do this deprecation in stages:

1. Emit an AzDO warning (builds will succeed): pipelines: Stage 1 deprecation of old azure-pipelines templates (emit AzDO warning) #2353
2. Emit an AzDO error, but with continueOnError: true (builds will "partially succeed")
3. Emit an AzDO error, but with continueOnError: false (builds will fail at run time)
4. Delete the pipelines (builds will fail at queue time)