[SVLS-6337] Don't spawn agent process if DD_AZURE_RESOURCE_GROUP not set for Azure flex consumption functions

[kathiehuang]

What does this PR do?

Adds a check to see if we are in an Azure function that is on the flex consumption plan and doesn't have the DD_AZURE_RESOURCE_GROUP env var set. If so, return before the agent process can be spawned.

• We updated the libdatadog Azure metadata detection logic to check for the resource group similarly, as well as serverless-components/datadog-trace-agent to shut down the trace agent if the resource group can't be determined

Motivation

• Currently the aas.resource.group span attribute for functions on flex consumption plans is set incorrectly in Datadog - they're all set to "flex"
  • This is important to fix because aas.resource.id is built using aas.resource.group, and the resource id is used in billing, which needs to be accurate
  • We had to figure out what to do if a customer who is using Datadog to monitor their Azure function on a flex consumption plan doesn't set the DD_AZURE_RESOURCE_GROUP env var. Rather than handling that in libdatadog, we decided to do it at a higher level in the trace agent to inform the customer of the error while shutting down the trace agent gracefully and preventing any traces from being sent to Datadog, as well as adding this in the serverless-compat layers to have defense in depth

Jira Ticket

Describe how to test/QA your changes

1. Clone serverless-components and update the commit hash in datadog-trace-agent/Cargo.toml
   everywhere that libdatadog is used to the most recent commit hash of the PR in libdatadog (currently d1b35ef21fff3c4588073504905081c8923bbc4b)
2. Follow the instructions in the Serverless Compatability Layer docs to build the Rust binary
3. Deploy an Azure function on flex consumption plan using the terraform tool, setting use_serverless_compat_local_path to true and making sure the built binary is in your python folder
4. Hit an endpoint in your function or wait a minute for the invoker to invoke your function and check the Datadog traces for your function. Without the DD_AZURE_RESOURCE_GROUP env var, you should see no traces
5. Go to Settings > Environment Variables in the Azure Portal for your function and add DD_AZURE_RESOURCE_GROUP as an environment variable with your resource group. Repeat step 4, you should see the correct resource group in the resource.group span attribute!

[kathiehuang]

@codex review

[chatgpt-codex-connector]

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[kathiehuang]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. 🚀

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[duncanpharvey]

Looks good just one nit!

[kathiehuang]

/merge

[dd-devflow-routing-codex]

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2025-10-02 15:05:56 UTC ℹ️ Start processing command /merge

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2025-10-02 15:06:02 UTC ℹ️ MergeQueue: pull request added to the queue

The expected merge time in main is approximately 0s (p90).

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2025-10-02 15:47:54 UTC ⚠️ MergeQueue: This merge request build was cancelled

kathie.huang@datadoghq.com cancelled this merge request build

[kathiehuang]

/remove

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2025-10-02 15:47:49 UTC ℹ️ Start processing command /remove

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2025-10-02 15:47:52 UTC ℹ️ Devflow: /remove