osd_types::osd_stat_sum_t: fix floor for num_objects_omap

Introduced in a130a4452e4fb159dc62fb417077d98dc9ebd621
Signed-off-by: Samuel Just <sam.just@inktank.com>
OSD: split pg stats during pg split

Fixes: #8020
Signed-off-by: Samuel Just <sam.just@inktank.com>
ReplicatedPG::hit_set_persist: clean up degraded check

Signed-off-by: Samuel Just <sam.just@inktank.com>
osd: track the number of hit_set archive objects in a pg

Also, use this value in agent_choose_mode instead of the max
number.

Related: #8124
Signed-off-by: Samuel Just <sam.just@inktank.com>