print current_rss info in mi_stats_print

It seems mimalloc only print peak_rss(it seems kind of misleading that it use "rss" other than "peak_rss" in log https://github.com/microsoft/mimalloc/blob/main/src/stats.c#L367) in `mi_stats_print`, and `current_rss` seems also useful and worthy to print out too.

Open src/stats.c around line 367 and inspect mi_stats_print and the existing peak_rss reporting. Trace how current_rss is obtained, then make the printed labels distinguish current_rss from peak_rss; done means mi_stats_print reports both values without making rss ambiguous.

Written by the indexing model from the issue text.