Document xpack.security.dls.bitset.cache settings (#44100)
Document xpack.security.dls.bitset.cache settings (#44100)

Two new settings were introduced in #43669 (bb130f5) to control the
behaviour of the Document Level Security BitSet cache.

This change adds documentation for these 2 settings.
gingerwizard/elasticsearch,uschindler/elasticsearch,uschindler/elasticsearch,uschindler/elasticsearch,nknize/elasticsearch,robin13/elasticsearch,coding0011/elasticsearch,coding0011/elasticsearch,gingerwizard/elasticsearch,HonzaKral/elasticsearch,gingerwizard/elasticsearch,GlenRSmith/elasticsearch,gingerwizard/elasticsearch,GlenRSmith/elasticsearch,scorpionvicky/elasticsearch,gingerwizard/elasticsearch,uschindler/elasticsearch,GlenRSmith/elasticsearch,scorpionvicky/elasticsearch,nknize/elasticsearch,scorpionvicky/elasticsearch,scorpionvicky/elasticsearch,scorpionvicky/elasticsearch,robin13/elasticsearch,robin13/elasticsearch,nknize/elasticsearch,uschindler/elasticsearch,robin13/elasticsearch,coding0011/elasticsearch,nknize/elasticsearch,coding0011/elasticsearch,HonzaKral/elasticsearch,HonzaKral/elasticsearch,nknize/elasticsearch,GlenRSmith/elasticsearch,gingerwizard/elasticsearch,GlenRSmith/elasticsearch,coding0011/elasticsearch,HonzaKral/elasticsearch,robin13/elasticsearch,gingerwizard/elasticsearch