[9.5](backport #7424) fix(azure): drive Resource Graph pagination by SkipToken, not ResultTruncated

[mergify]

Summary

Most Azure subscriptions in CSPM scans were showing only subscription-level findings, with zero resource-level findings (storage accounts, VMs, key vaults, etc.). Root cause: cloudbeat's Azure Resource Graph (ARG) pagination loop stopped after the first page of results on every real-world query, silently dropping resources per scan cycle.

Root cause

In internal/resources/providers/azurelib/inventory/resource_graph_provider.go, runPaginatedQuery broke out of its pagination loop whenever response.ResultTruncated == false. That flag does not mean "no more pages" — per Microsoft's Resource Graph pagination contract, SkipToken presence/absence is the only reliable continuation signal. In practice, ordinary paginated ARG responses report ResultTruncated: false even when a valid SkipToken for the next page is present, so the loop always exited after page 1.

Fix

Pagination now continues based solely on whether SkipToken is empty, matching Microsoft's reference pagination pattern, instead of trusting ResultTruncated.

Regression test

Added a test in internal/resources/providers/azurelib/inventory/resource_graph_provider_test.go that mocks a 3-page ARG response sequence where every page reports ResultTruncated: false but carries a SkipToken until the final page. It fails against the pre-fix code (only page 1's asset is returned) and passes with the fix.

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This is an automatic backport of pull request #7424 done by Mergify.