overzooming tiles in studio not reporting correct zxy in deubg mode

[isiyu]

mapbox-gl-js version: latest in mapbox-studio

in studio when you turn on debug mode the z/x/y helper doesn't update after z16; guessing it is reflecting the data that is being displayed, and at z16+ its still displaying data from z16 mvt. which makes sense, but showing a corresponding z## with that x,y coordinate can cause confusing.

dropping ticket here, per @samanpwbb this is a bug in gl-js and not studio

Steps to Trigger Behavior

1. turn on debug->tile boundaries in Mapbox studio
2. zoom in past z16+

Expected Behavior

debug's tile coordinates for x,y at z16+ reflect the z16 tile

Actual Behavior

label debug tiles with z16 consistently since that's the vt's data that's being show or to update to proper z-x-y coordinates in debug mode