go: expose process_vm_access events and statistics

[Aegrah]

Part 3 of 3, bottom-up: private probes → public event and tests → Go bindings.

Summary

Expose process_vm_access records, queue/event flags, snapshot statuses and correlation-map failure statistics in Go. Preserve signed syscall returns and validity fields so consumers can distinguish unresolved identity and incomplete snapshots.

Issue: https://github.com/elastic/endpoint-dev/issues/21204

Validation

Preflight: 20260916-pva-v2-release-final. Fleet acceptance: 20260916T172021Z-process-vm-access, accepted build endpoint-9.4.2-5564d77d41a8132d (Stack/Agent/Endpoint 9.4.2). Main integration was validated separately. Full persona-volume gate explicitly waived by the user; no production-volume claim.

Go tests pass on x64 and ARM64. Sensor validation belongs to the preceding two layers; no additional kernel hook is introduced here.

Companions: elastic/endpoint-package#800 · https://github.com/elastic/endpoint-dev/pull/22027

[Aegrah]

Merge-forward of the #428 valgrind fix-up (7a5bdd7); no change of its own.