CosmosDB: define applicable values for db.operation.name and add proper reference to az.namespace

[lmolkova]

• List operations names for Cosmos DB clients.
• Lowercase operation_type value.
• Add az.namespace attribute and reference it (previously undefined, but referenced in md)
• Clean up examples

Merge requirement checklist

• CONTRIBUTING.md guidelines followed.
• Change log entry added, according to the guidelines in When to add a changelog entry.
  • If your PR does not need a change log, start the PR title with [chore]
• schema-next.yaml updated with changes to existing conventions.

[FabianMeiswinkel]

I think transactional batch but especially bulk needs some more thoughts. Bulk operations are done fundamentally differently in Java and .Net. In Bulk there is an explicit API for executing a set of operations as bulk - so something like execute_bulk would probably be good? In .Net whether point operations are executed as bulk or normally depends on some config on the client - which right now you result in create or read covering operations that are actually executed as part of a bulk operation and would have completely different non-functional characteristics like perf.

[jcocchi]

Looks good to me! Left one minor comment

[FabianMeiswinkel]

LGTM - Thanks!