feat: expand built-in log format library

[mpryor]

Summary

Expand the built-in log format library from 19 formats to cover more common log sources.

Problem

nless currently auto-detects 19 log formats. lnav ships with 70+. More built-in formats means more "it just works" moments where users pipe in logs and get instant columnar parsing.

Candidate formats to add

• Databases: MySQL slow query, PostgreSQL, Redis, MongoDB
• Web servers: Caddy, HAProxy, AWS ALB/ELB
• Cloud: AWS CloudTrail, GCP audit logs
• Containers: Docker daemon logs, containerd
• CI/CD: GitHub Actions, Jenkins
• Languages: Java (log4j2 patterns), Rust tracing, Go structured logging (zerolog, zap)
• System: journald, macOS unified logging, Windows Event Log (exported)
• Network: Bro/Zeek TSV

Technical Considerations

• Each format is a named regex with capture groups in logformats.py
• Priority scoring ensures the most specific format wins
• Community contributions welcome — format definitions are self-contained
• Consider supporting a user-contributed format registry

Related

• Existing formats defined in nless/logformats.py
• P key for manual log format selection