Support higher zoom levels (increase 25.5 max zoom to 28.0)

Nobody has claimed this yet.

## Motivation

We want to show high precision GPS measurements as points. Normally, zoom level of 25.5 is enough for even the most precise measurements, however we want to be able to zoom in more to clearly see error distribution. Say we measure the same point 100 times. In a perfect world that would be 100 duplicates of the same point but GPS measurements have some error. At zoom level of 25.5, errors are visible but points are rather too close to each other to clearly see the error distribution.

OpenLayers and ArcGIS runtime SDK both support higher zoom levels.

## Implementation

Not sure. Probably just increase a constant number defined somewhere in the code.

I believe the reason for using 25.5 as the maximum allowed zoom was to fit it into 1 byte (255 each 0.1). This was a long time ago, [see](https://github.com/mapbox/mapbox-gl-js/issues/251). Is it still necessary to fit zoom into 1 byte? As far as I could tell, zoom is not being put into every vertex anymore.

Supporting zoom levels higher than 28.0 might not be straightforward due to floating point precision, but 28.0 shouldn't be much of a challenge as long as the 1-byte requirement isn't a thing anymore.

Start by locating the constant or validation that limits the maximum zoom to 25.5, then inspect whether zoom is still encoded in one byte or stored in vertex data. Done means zoom level 28.0 is accepted and high-precision points can be viewed at that level without breaking existing map behavior.

Written by the indexing model from the issue text.