Log performance details

To help debugging (production) environment issues, we should log memory usage, GC pauses, etc. We can have a configuration option `:log-performance-details` to log these often. We can log some details seldomly (like once an hour) and with the flag set like every minute or what is useful.

API would be nice for this, because it can be added to external tools/dashboards.

The issue names no files, tests, or entry points; start by locating the project's logging and configuration code, then identify where runtime memory and GC metrics can be gathered. Clarify the sampling intervals, the `:log-performance-details` behavior, and the API shape before implementation; done means periodic logs and an external-tool-friendly API are specified and tested.

Written by the indexing model from the issue text.