Start building PublicState module to centralize data preparation for updates

[#84523966]
Add public state function for bullets as well

[#84523966]
Altered public state computation to return a tuple with ID as first value

[#84523966]
Refactor public_state_test for better fixturing
Extract generation of tank list public state to PublicState

[#84523966]
Factor out bullet fixture to a method

[#84523966]
Implemented bullet list reporting in PublicState

[#84523966]
Extracted private tank state reporting to a separate module
[#84523966]
Bullets and tanks are now showing.

[#84523966]
Remove debugging output.  Allow game window to run in background to enable multiplayer testing.

[Finishes #84523966]