Better Debug support for Bevy ECS

[alice-i-cecile]

What problem does this solve or what need does it fill?

Debugging and troubleshooting ECS problems in

Describe the solution would you like?

Derive Debug for query filters, World, App, AppBuilder etc.

Describe the alternative(s) you've considered?

Write custom wrappers every time to extract and then display the information that I care about each time that I'm debugging these parts of the core logic.

Additional context

Creating a sensible debug output for some of the larger objects (like App and World) seems challenging; a pattern for doing so in a more / less verbose fashion would be welcome.

[alice-i-cecile]

This is improved by #1525, with a Debug impl for World.

[targrub]

@alice-i-cecile What remains to be coded to complete this issue for now?

[alice-i-cecile]

I would like debug impls for:

• World
• App
• Query
• QueryState

Once that's done I think we can close this out in favor of more specific issues.

[targrub]

I'll take a look to see if I can do any of those.

[alice-i-cecile]

WRT App, don't worry about doing anything fancy for the Schedule. We can and should wait until after the stageless rewrite settles.