DB/Misc: Make invisible some visible Triggers

By untaught, closes #10648
DB/Misc: Fixes 2 innkeepers of Hallow's End event

By dr-j and untaught, closes #11108
DB/Misc: Quest item "Drain Schematics" drop

By trickerer, fixes #10394
DB/SAI: Sprouted Frond

By untaught, closes #11123
DB/SAI: Slaves of the Stormforged

By untaught, closes #10509
Merge https://github.com/TrinityCore/TrinityCore