[filebeat][fix] include ESStorageExtension identity in state store cache key

[barkhayot]

• issue [bug-hunter] Filebeat state store cache key ignores storage extension and mixes receiver state #49656
• when openStateStore is called with different ESStorageExtension instances but the same backend/path, the global registry cache (globalStores) was keyed only by backend://path. The second caller would reuse the first caller's esRegistry, causing cross-receiver state leakage
• append the extension's pointer address (%p) to the cache key when ESStorageExtension is non-nil, ensuring each distinct extension gets its own sharedRegistries entry
• add suggested test in issue

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📥 Commits

Reviewing files that changed from the base of the PR and between dd39290 and f916f64.

📒 Files selected for processing (2)

• filebeat/beater/store.go
• filebeat/beater/store_test.go

✅ Files skipped from review due to trivial changes (1)

• filebeat/beater/store_test.go

🚧 Files skipped from review as they are similar to previous changes (1)

• filebeat/beater/store.go

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📝 Walkthrough

Walkthrough

The changes modify storeKey to include the Elasticsearch storage extension identity when non-nil, appending an |esext:%p segment to the generated key. openStateStore now passes cfg.ESStorageExtension into storeKey, so global store reuse/splitting also depends on the specific ES storage extension instance. A test was added that opens two stores with identical configs except for different ESStorageExtension instances and verifies that state written to one is not visible from the other.

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