Refactor rep_hist_format_hs_stats() to add noise when counters are initialised
This makes the code shorter, and the security guarantees easier to reason about (it's how experimental privcount does it).
See #23414 (moved) for background.
This makes the code shorter, and the security guarantees easier to reason about (it's how experimental privcount does it).
See #23414 (moved) for background.