io/storage: add JSON support

Bincode can't deal with a number of serde's features that would be
desirable if we're using the same Serialize impls for generating JSON
data for the viewer.

src/core/region_processor.rs

@@ -148,6 +148,7 @@ impl<'a> SingleRegionProcessor<'a> {
 		storage::write_file(
 			&self.output_path,
 			&self.processed_region,
+			storage::Format::Bincode,
 			REGION_FILE_META_VERSION,
 			self.input_timestamp,
 		)

src/core/tile_renderer.rs

@@ -105,7 +105,8 @@ impl<'a> TileRenderer<'a> {
 
 		region_loader
 			.get_or_try_init(|| async {
-				storage::read_file(&processed_path).context("Failed to load processed region data")
+				storage::read_file(&processed_path, storage::Format::Bincode)
+					.context("Failed to load processed region data")
 			})
 			.await
 			.cloned()