DB/SAI: Kill SAI Errors

NPCS in Sunken temple do not need difficulty flags as there is only one mode
Merge branch 'master' of https://github.com/TrinityCore/TrinityCore into Transmogrification
更新
更新
Merge branch 'Transmogrification' of https://github.com/shenhuyong/TrinityCore into ghbb
DB/Spells: added a few spells to spelldifficulty_dbc
[TW363] - Core/Spells: The needed hacks for yesitsme's Mimiron spellscripts
[TW364] Scripts/Ulduar: Solve issue added recently with permanent frost bombs
Core/Maps: Don't use EnsureGridCreated_i() for base map in Map::LoadMap, use EnsureGridCreated() which is thread safe because although the LoadMap() call probably came from a thread safe EnsureGridCreated() call from the current map instance, multiple map instances can load grids for the same base map in the same time, and each of them has it's own mutex, therefore we should rely on the basemap's mutex
DB/Fishing: Add fishing level to Undercity

By AriDEV, closes #12929
DB/SAI: Some corrections

Wiki said despawn time for gobjects spawned using smart action 50 was in ms, which was wrong its actually in seconds,
Scripts: Correct despawn time of multiple objects

WorldObject::SummonGameObject respawn time is in seconds and not milliseconds
Scripts/BladesEdge: Fix a typo introduced in 430b3ad

Thanks @Nihilianth
Merge branch 'master' of https://github.com/TrinityCore/TrinityCore into ghbb
Merge branch 'master' of https://github.com/TrueWoW/TrinityCore into ghbb

Conflicts:
	src/server/game/Spells/SpellMgr.cpp
	src/server/scripts/Custom/Ulduar/TW_boss_mimiron.cpp