debian/config: Enable DAMON_STAT for memory access statistics collection

The current Debian kernel already enables the DAMON framework and key features like DAMON_RECLAIM and DAMON_LRU_SORT. However, utilizing the raw monitoring data provided by DAMON for system-wide analysis can require complex setup and interpretation of the results.

CONFIG_DAMON_STAT provides DAMON_STAT, an in-kernel solution that automates this process. This module automatically runs DAMON for the entire physical memory of the system and summarizes the results into easy-to-understand statistical metrics. This specifically includes estimated memory bandwidth (hotness) and memory idle time percentiles (coldness).

This feature is designed to be always-on in production environments. It balances accuracy and performance by auto-tuning monitoring intervals. According to real-world tests cited in the upstream documentation[1], it typically consumes less than 1% of a single CPU's time ("0.x % single CPU time").

Enabling this option greatly helps system administrators and developers to more easily understand memory behavior, identify bottlenecks, and find opportunities for memory management optimization, especially on large-scale systems.

Even when built into the kernel by setting CONFIG_DAMON_STAT=y, its operation can be controlled at runtime or boot time via the 'damon_stat.enabled' module parameter.

[1] https://docs.kernel.org/next/admin-guide/mm/damon/stat.html

Signed-off-by: Yunseong Kim ysk@kzalloc.com