Forward MSAL client metadata headers through IMDS to ESTS

[Copilot]

IMDS cannot forward client telemetry to ESTS because MSAL Python never sends it. Adds three headers to IMDSv1 managed identity token requests, matching the .NET implementation (PR #5912).

Changes

• msal/managed_identity.py: Added x-client-SKU, x-client-Ver, and x-ms-client-request-id headers to _obtain_token_on_azure_vm(). Uses x-ms-client-request-id (not client-request-id) as IMDS requires the x-ms- prefix.

headers={
    "Metadata": "true",
    "x-client-SKU": SKU,
    "x-client-Ver": __version__,
    "x-ms-client-request-id": str(uuid.uuid4()),
},

• tests/test_mi.py: Updated three existing IMDS test assertions (test_happy_path_of_vm, test_happy_path_of_pod_identity, test_vm_resource_id_parameter_should_be_msi_res_id) to expect the new headers. SKU is validated against a hardcoded "MSAL.Python" constant; correlation ID is validated as a well-formed UUID.

Scoped to IMDS only — no changes to App Service, Arc, CloudShell, Machine Learning, or Service Fabric sources.

[Copilot]

Pull request overview

Adds MSAL client metadata headers to IMDS (Azure VM / Pod Identity) token requests so IMDS can forward client telemetry to ESTS.

Changes:

• Add x-client-SKU, x-client-Ver, and x-ms-client-request-id headers to IMDS managed identity token requests.
• Update IMDS-related unit tests to assert the presence of these headers and validate the request-id as a UUID.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
msal/managed_identity.py	Injects MSAL SKU/version and a per-request UUID into IMDS request headers.
tests/test_mi.py	Updates IMDS tests to expect the new headers and validates the UUID format.

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