[improve] PIP-467: Adopt slog for structured logging across Pulsar

[merlimat]

Motivation

Pulsar currently uses SLF4J with string-interpolated log messages, making it difficult to query, filter, and
correlate log data in production environments. PIP-89 previously approved adopting structured logging but the
chosen approach (an in-repo custom library) had limitations.

This PIP proposes adopting slog as a lightweight, high-performance structured
logging facade that integrates with existing Log4j2/SLF4J backends.

Key features

• Fluent API with structured key-value attributes
• Derived loggers with persistent context
• Context composition across component boundaries (e.g., Pulsar → BookKeeper)
• Zero-allocation disabled path (2.4× faster than Log4j2, 2.8× faster than SLF4J)
• @CustomLog Lombok integration
• Auto-detection of Log4j2 or SLF4J backend

PoC

The managed-ledger module has been fully migrated as proof of concept:
merlimat#20

cc @apache/pulsar-committers

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