Core/SmartAI: Implement SMART_TARGET_CLOSEST_ENEMY (25)

Required for upcoming EAI to SAI conversion.

Closes #10482
Scripting/Sethekk Halls: Move Boss Anzu from EAI to CPP and some cleanup.
DB: Fix startup errors
Scripts/DrakTharonKeep: update Trollgore

Closes #10453

Signed-off-by: joschiwald <joschiwald@online.de>
DB/SAI: Fix quest Killing Two Scourge With One Skeleton

Closes #10475
DB/Misc: Add Dregbar Runebrand pathing

Closes #10476
DB/SAI: Fix quest Fueling the Project (11715)

Closes #10477
DB/SAI: Fix quest Strengthen the Ancients (12092)

Closes #10478
DB/SAI: Fix quests See You on the Other Side (12121) and Jin'arrak's End (12152)

Closes #10480
Closes #4552
DB/SAI: Fix quest From Whence They Came

Closes #6525
DB/SAI: Fix quest Magic Carpet Ride

Initial Magic Carpet Ride fix: 820ce262779c05a95649f

Closes #10328
DB/NPCs: Correct faction of Seeping Ooze

Closes #10375
DB/SAI: Script Itharius

Closes #10401
DB/NPCs: Because of some silly reason there are NPCs with AIName 0
DB/SAI: Fix a typo in a SAI script, fixes quest Bring Me The Egg!

Closes #10415
DB: Fix a db startup error
Merge branch 'master' of github.com:TrinityCore/TrinityCore into 4.3.4