general: Name spawned threads

This is for easier debugging in case a panic happens -
instead of dealing with "thread <unnamed> paniced...", etc.,
we get a name relevant to our context.

src/widgets/image_page.rs

@@ -152,7 +152,9 @@ impl LpImagePage {
 async fn load_texture_from_file(file: &gio::File) -> Result<gdk::Texture, glib::Error> {
     let (sender, receiver) = futures_channel::oneshot::channel();
 
-    std::thread::spawn(clone!(@weak file => move || {
+    let _ = std::thread::Builder::new()
+        .name("Load Texture".to_string())
+        .spawn(clone!(@weak file => move || {
             let result = gdk::Texture::from_file(&file);
             sender.send(result).unwrap()
         }));

src/widgets/properties_view.rs

@@ -377,7 +377,9 @@ impl LpPropertiesView {
 async fn parse_svg_file_future(path: std::path::PathBuf) -> anyhow::Result<svg_metadata::Metadata> {
     let (sender, receiver) = futures_channel::oneshot::channel();
 
-    std::thread::spawn(move || {
+    let _ = std::thread::Builder::new()
+        .name("Parse SVG".to_string())
+        .spawn(move || {
             let result = svg_metadata::Metadata::parse_file(path);
             let _ = sender.send(result);
         });