Core/Spells: if for TARGET_UNIT_MASTER owner aquire fails, try to retrieve owner by using TempSummon

[sanctum32]

Changes proposed:

This PR allows to gather owner for TARGET_UNIT_MASTER by using TempSummon if by some case function "GetCharmerOrOwner()" fails to retrieve owner

Issues addressed: Fixes #

Tests performed: (Does it build, tested in-game, etc)

• Build on WIndows 11 64bit (MSVC) & Fedora 38 64bit (GCC)
• Mainly tested with https://www.wowhead.com/quest=14416/the-hungry-ettin, where horses (temp summons) casts 68917 spell for quest credit (unpublished quest script)

Known issues and TODO list:

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[Ovahlord]

This PR is conflicting with the upcoming tempsummon rework.

Furthermore GetOwner() is only meant to return the unit that is specified in UNIT_FIELD_SUMMONEDBY which is set for summons listed unter SummonPropertiesControl::Pet.

TARGET_UNIT_MASTER is only meant to work with charmed units and controlled pets, so the spell should actually target GetCharmerOrOwner(). If that one fails that getter needs to be investigated