Move buffer stats to a separate debug page

[lucaswoj]

I want to keep the index.html debug page simple. "debug" and "collision debug" modes can stay.

[mourner]

That would be great! I'd also remove the random points geojson and leave only the route one.

[bhousel]

Worth mentioning - I was thinking of adding an "events debug" too.

I don't mind having buffer stats there. Honestly I'd prefer to have all the debug things consolidated in one control rather than spread across different pages - but no strong opinion on this.

[lucaswoj]

I often use debug/index.html to build ephemeral testing "rigs". For that use-case, having a simple page possible is ideal (i.e. new mapboxgl.Map(...) and nothing else).

Some testing rigs are worth checking in and reusing, like "buffer stats." Keeping those rigs on separate pages

• frees us from having to build and maintain any enable / disable UI
• frees testing rigs from having to "play nicely" with other rigs on the same page, allowing more "radical" setups (i.e. requireing and manipulating internal modules directly or displaying custom UI elements)
• scales infinitely with the number of testing rigs we create

[mourner]

I agree with @lucaswoj — when I'm debugging a particular feature, I'll usually start by removing everything but the barebones code from site.js and start from there. It's cumbersome to do every time, so having a nice default simple debug page would be a time saver.

[bhousel]

Wouldn't it be better if the debugging things were contained in a Control like:

map.addControl(new mapboxgl.Debug({position: 'top-left'}));

I agree index.html and site.js ideally shouldn't have this extra code.

[mourner]

-> #3596