[DOCS] Document `thread_pool` node stats (#50330)
[DOCS] Document `thread_pool` node stats (#50330)



HonzaKral/elasticsearch,HonzaKral/elasticsearch,uschindler/elasticsearch,GlenRSmith/elasticsearch,gingerwizard/elasticsearch,scorpionvicky/elasticsearch,gingerwizard/elasticsearch,nknize/elasticsearch,robin13/elasticsearch,gingerwizard/elasticsearch,GlenRSmith/elasticsearch,GlenRSmith/elasticsearch,gingerwizard/elasticsearch,HonzaKral/elasticsearch,scorpionvicky/elasticsearch,uschindler/elasticsearch,gingerwizard/elasticsearch,robin13/elasticsearch,robin13/elasticsearch,robin13/elasticsearch,nknize/elasticsearch,HonzaKral/elasticsearch,uschindler/elasticsearch,uschindler/elasticsearch,nknize/elasticsearch,GlenRSmith/elasticsearch,gingerwizard/elasticsearch,scorpionvicky/elasticsearch,scorpionvicky/elasticsearch,nknize/elasticsearch,scorpionvicky/elasticsearch,robin13/elasticsearch,gingerwizard/elasticsearch,GlenRSmith/elasticsearch,nknize/elasticsearch,uschindler/elasticsearch