Core/Misc: Fix typo

Fix typos about the word "Resurrect"
Core/Spells: Sniper Training should refresh every 6 seconds if all conditions are met
Core/Auras: Solve exploit involving SPELL_AURA_MOD_DAMAGE_DONE and weapon swapping
Core/NetworkIO: Improve packet spam solution

Implement an improved packet Anti-DoS by counting how many times the same opcode has been sent in the last second and applying the policy specified in the configs if the amount of packets exceeds a reasonable amount.
Credits to the original author who decided to share this with TrinityCore team.
Merge pull request #12120 from Trisjdc/aura_exploit

Core/Auras: Solve exploit involving SPELL_AURA_MOD_DAMAGE_DONE and weapon swapping
Merge pull request #12119 from Trisjdc/sniper_training

Core/Spells: Sniper Training should refresh every 6 seconds if all conditions are met