minedmap: store region list in BTreeSet

We want to have a sorted list in the end anyways to make metadata
generation deterministic, and we don't have to worry about deduplication
of coordinates when generating mipmap tile lists.

src/bin/minedmap/tile_renderer.rs

@@ -80,10 +80,10 @@ impl<'a> TileRenderer<'a> {
 		})
 	}
 
-	pub fn run(self, regions: &[TileCoords]) -> Result<()> {
+	pub fn run(self, regions: impl IntoIterator<Item = TileCoords>) -> Result<()> {
 		fs::create_dir_all(&self.config.map_dir)?;
 
-		for &coords in regions {
+		for coords in regions {
 			if let Err(err) = self.render_tile(coords) {
 				eprintln!("Failed to render tile {:?}: {:?}", coords, err,);
 			}