Add a first-party schedule visualizer

[ItsDoot]

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

In traditional OOP-based game development, per-frame logic flow is generally easier to deduce because (usually) the call-stack is the schedule. We don't have that luxury with today's data driven scheduling mechanism.

What solution would you like?

A way to visualize the schedule graph with all ordering constraints displayed. This could (and should) be part of the Bevy Editor when we get there, but a first-party solution now would also be nice.

Recommended Features:

• Viewing individual Schedules.
• Searching by System Sets and Systems to see their scheduling constraints.
• See which Plugins registered which Schedules, System Sets, and Systems.
  • Also extend this to registered hooks and observers, if possible.
• Live visualization of the schedule graph, with the ability to freeze the visualizer at any point for review.
• Breakpoint-style visualization freezes whenever a Schedule is modified.

Those last two will be very important for debugging if/when we get runtime schedule modification.

What alternative(s) have you considered?

Continue using bevy_mod_debugdump as-is.

Additional Context

Prior Art: bevy_mod_debugdump

[james7132]

Might be a good idea to add it to CI and serve it up on https://dev-docs.bevyengine.org/ like https://jakobhellermann.github.io/bevy_mod_debugdump/ that is always kept up to date with main.