Move Strings methods
Move Strings methods

lib: Moved unsafe String extension methods from `Strings` to the `UnsafeStrings` extension.
lib: Moved character-based String extension methods from `Strings` to the `StringChars` extension.
lib: Added the `StringCodePoints` extension.
lib: Deprecated the `String.size` method.

Clashsoft/Dyvil,Clashsoft/Dyvil