* Core/Pets: Pet management refactoring
* Preload basic pet data on character login with async query
* Load additional pet data (declined names/auras/spells/cooldowns) using async query after we are sure pet loading will succeed
* Remove all select queries related to pet stable/unstable
* Remove all silent pet deletions except explicit UI-triggered abandons
* Fixed displaying stable master content when current pet is not summoned
* Allow to stable/swap unsummoned current pet
Closes#3610Closes#21266
(cherry picked from commit 5c1fc5e387)