[Slayers] System redesign

[BigloBot]

Updates the slayer system

• Has a singleton slayer class
• Updated dynamically when scoreboard updates
• Updates existing slayer stuff to use Slayer Singleton
• Improves SlayerBossBar in cases where armour stand takes a little longer to spawn and the player has already damaged boss causing % to be slightly off (most noticible on lower hp slayers)
• Reduce range and add additional health check in an attempt to reduce false positives to Fire Pillar Announcer
• Adds Glow Colour Option