make TileID more similar to -js's TileCoord

[ansis]

• x values are wrapped by worlds in -js but not in -native
• w value doesn't make sense in -native
• names are different

[jfirebaugh]

Regarding tile wrapping, the changes I would like to see are:

• Two different types: TileID (wrapped x coordinate; prefer this type unless you specifically need an unwrapped ID) and UnwrappedTileID (unwrapped x coordinate + w)
• UnwrappedTileID has TileID wrap() const method; no other conversions are available
• tileCover returns UnwrappedTileIDs
• Remove Source::getLoadedTiles() and Source::getTiles()
• Add Source::getCoveringUnwrappedTileIDs(), Source::getTile(const TileID&) and maybe Source::getTile(const UnwrappedTileID&)
• Change TransformState::matrixFor parameter to UnwrappedTileID
• Fix ripples from those changes

[jfirebaugh]

The names TileCoordinate and UnwrappedTileCoordinate would be ok with me too, but we'll need to clear away the existing TileCoordinate type first.

[jfirebaugh]

⇢ #3834