refactor: add promisified wrapper for MBTiles

[akx]

This adds a small wrapper around the @mapbox/mbtiles MBTiles class to promisify opening them (instead of callback pyramids).

This opens up avenues to further DRY out the code and make things more async and modern.

[akx]

Okay, rebased post #1320 merge.

[akx]

ping @acalcutt :)

[acalcutt]

Overall I do think this looks cleaner and I am likely going to merge this.

This one thing I am wondering about id the file name of the wrapper. It seems like pmtiles_adapter.js and mbtiles_wrapper.js should be named more similarly. That is just really a nitpick thing.

Speaking of pmtiles, I probably did not promisify it very well, so I am wondering if you think there are any improvements there with pmtiles like these changes.

[akx]

This one thing I am wondering about id the file name of the wrapper. It seems like pmtiles_adapter.js and mbtiles_wrapper.js should be named more similarly. That is just really a nitpick thing.

Maybe. I just named the file after the class name, and the class really is just a simple wrapper around MBTiles :)

[acalcutt]

Looks cleaner to me. Tested it locally and it seems to work fine

In the future we might want to look at renaming a few of these files, but we can think about it more.