Make TimeSync a Unity Singleton

[LiamOverett-AMRC]

Changed how TimeSync behaves so only one instance of that object can exist in a scene at any given time. This fits with the "one source of truth" for timestamps across Unity projects. Also gave the Unity programmer the option to make the TimeSync object non-destroyable between scene changes.

Changes:

• Update TimeSync to be a 'true' Unity singleton that will destroy itself if other instances of that object already exist in the scene
• Add option to make a TimeSync object non-destroyable between scene changes
• Update BaseOutlet to reference the update TimeSync singleton
• Update the package version from 1.16.0 to 1.16.1 to reflect the changes