[tls_mgm] Export active TLS connection statistics

[darwvin-dev]

Summary

Export active TLS connection gauges from tls_mgm so operators can monitor negotiated TLS versions, peer verification state and cipher families through the standard OpenSIPS statistics interface / Prometheus exporter.

Statistics

• tls_mgm:connections
• tls_mgm:tls_v1_0_connections
• tls_mgm:tls_v1_1_connections
• tls_mgm:tls_v1_2_connections
• tls_mgm:tls_v1_3_connections
• tls_mgm:peer_verified_connections
• tls_mgm:peer_unverified_connections
• tls_mgm:aes_gcm_connections
• tls_mgm:chacha20_connections
• tls_mgm:other_cipher_connections

Implementation

The gauges are computed from TLS metadata already cached on active tcp_connection objects. A generic TCP traversal helper holds one partition lock at a time while invoking a read-only callback. This avoids counter drift and avoids adding work to the TLS handshake hot path. Exact cipher names are grouped into stable cipher families instead of creating unbounded dynamic statistic names.

Validation

• make include_modules="tls_mgm tls_openssl proto_tls" modules -j8 — passed
• make app -j8 — passed
• git diff --check — passed

Refs #3315

Safety / validation update

The TCP traversal now ignores non-TLS/WSS connections before interpreting shared_data as tcp_tls_info. This keeps the generic TCP shared_data slot type-safe for other protocols while preserving TLS and WSS statistics.

Revalidated after rebasing onto current master:

• make include_modules="tls_mgm tls_openssl proto_tls" modules -j$(nproc) — passed
• make app -j$(nproc) — passed
• git diff --check — passed