Complete Ceph source registry coverage

[ktsaou]

Summary

• Completes the pinned Reef/Squid/Tentacle Ceph source registry extraction for the newly recovered RGW operation, topic, sync-delta, D4N, and simple-throttler surfaces.
• Adds source-complete synthetic fixtures for the new branches, including gateway/no-gateway messenger identity and simple-throttler reset behavior.
• Makes source-registry closure fail closed when candidate C/C++ registrations are omitted from the declared upstream paths and recognizes both dot and pointer registration calls.
• Adds repository-local Python bytecode ignore rules.

Validation

• python3 -m unittest discover -s prometheus/tools -p 'test_*.py' — 8/8 PASS.
• Pinned Ceph generator suite — 24/24 PASS.
• Regenerated SOURCE-REGISTRY.yaml is byte-for-byte identical.
• Independent Reef/Squid/Tentacle source cross-check reports zero unresolved families.

This testdata change is paired with netdata/netdata#23551 and should merge before the Netdata PR.