Modernize the codebase w/ Fixes & Optimizations

[kamronbatman]

Updates the codebase to the newest code paradigms and standards. This includes:

• Using string interpolations
• Removing default value initialization
• Merging sequential checks
• Using ?? (null coalescing) instead of ternary
• Using null propagation where possible
• Removing unused namespaces
• Using arrow body expressions for properties where applicable
• Using automatic property initializers
• Removing redundant initializers including delegations
• Removing implicit this
• Using constructor initializers
• Use type casting variables to stop double casting
• Remove overloading in favor of default value parameters
• Replace ArrayList, HashTable, and object[] states with typed collections.
• Use in-line out variable declaration
• Optimize the spell system by introducing a singular SpellTarget object and making all spells children of a TargetingSpell class. This reduces the number of internal target types and reuses code.
• Optimize GetEntities (GetItems[InRange] and GetMobiles[InRange]) to use generics where possible
• Update GetRegion to use generics
• Replace callbacks with object states with lambda curries
• Remove Timer.DelayCall generic TimerStateCallback in favor of lambdas/closure/curries

In Progress:

• Remove overloading in favor of named parameters
• Optimize GetEntities to take a flexible set of predicates so that items/mobiles are filtered in the LINQ
  • e.g. Extending SelectItems, SelectMobiles, SelectMultis, etc

PRs:
#1 - Updates code formatting, style, fixes various small bugs, and changes casts/type checks to use pattern matching
#3, #37- Updates out variables, adding items with optional parameters in ctor, and makes functions that take typeof variables use generics.
#7 - Fixes Dictionary uses throughout repo
#14 - More cleanup
#18 - Collapsing more null checks and removing overloading constructors
#31 - Fix comparables
#36 - Cleans up SpellTargeting