[monitor] Add trace preview atomic command models

[bragi92]

Corresponding Azure CLI Extensions pull request: Azure/azure-cli-extensions#10479

Summary

Add the 2026-09-03-preview atomic command models used by the distributed trace feature in application-insights version 2.0.0b3.

• Trace container create, show, and update models for the singleton default container. The CLI generator also derives the container wait command.
• Trace association create, show, list, and delete models at component, resource group, and subscription scope.
• Matching XML and JSON configurations for seven trace resource paths, plus the parent command-group indexes.
• Preview stages, the agreed container argument names, and container help/examples including retention and metrics billing defaults.

The scope-specific association models are consumed as unregistered atomic helpers by the extension's public az monitor trace-association commands, which dispatch based on --resource-uri. They do not introduce additional public scope-specific command groups in the extension.

This change intentionally excludes unused association update models, container deletion, and unrelated workspace, metrics, or issue APIs. Existing workspace command models are unchanged.

Validation

• Passed the repository's required full metadata check: aaz-dev command-model verify --aaz-path <checkout>.
• Regenerated the companion extension's trace commands from these models: all 15 atomic models produce the 16 committed generated command modules exactly, including the derived container wait command.
• Confirmed no unused association update models or empty default command subgroups remain.

Draft status

This is the companion metadata PR for coordinated review with Azure/azure-cli-extensions#10479. The extension PR owns orchestration, component flags, argument validation, destination reporting, tests, and packaging. Live ARM and trace-ingestion validation remain release gates in that implementation PR.