[.NET] Add support for .NET 9

[andrewlock]

What does this PR do? What is the motivation?

Update documentation about recently released support for .NET 9

Merge instructions

Merge queue is enabled in this repo. To have it automatically merged after it receives the required reviews, create the PR (from a branch that follows the <yourname>/description naming convention) and then add the following PR comment:

/merge

Additional notes

[andrewlock]

/merge

[dd-devflow]

Devflow running: /merge

View all feedbacks in Devflow UI.

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2024-11-19 12:31:02 UTC ℹ️ MergeQueue: waiting for PR to be ready

This merge request is not mergeable yet, because of pending checks/missing approvals. It will be added to the queue as soon as checks pass and/or get approvals.
Note: if you pushed new commits since the last approval, you may need additional approval.
You can remove it from the waiting list with /remove command.

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2024-11-19 16:31:10 UTC ⚠️ MergeQueue: This merge request was unqueued

This merge request was unqueued

[github-actions]

Preview links (active after the build_preview check completes)

Modified Files

• https://docs-staging.datadoghq.com/andrew/add-dotnet9/profiler/enabling/dotnet
• https://docs-staging.datadoghq.com/andrew/add-dotnet9/serverless/azure_app_services/azure_app_services_windows
• https://docs-staging.datadoghq.com/andrew/add-dotnet9/tracing/metrics/runtime_metrics/dotnet
• https://docs-staging.datadoghq.com/andrew/add-dotnet9/tracing/trace_collection/automatic_instrumentation/dd_libraries/dotnet-core
• https://docs-staging.datadoghq.com/andrew/add-dotnet9/tracing/trace_collection/compatibility/dotnet-core

[jhgilbert]

/merge

[dd-devflow]

Devflow running: /merge

View all feedbacks in Devflow UI.

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2024-11-20 16:16:04 UTC ℹ️ MergeQueue: pull request added to the queue

The median merge time in master is 28m.