fix(entries): stamp the sort key of entries

The sort-key of an entry was compared as written, without stamping the
values into it. Autoconfigured Linux entries all use "$kernel" as the
sort key, so they compared equal and kept the order the filesystem
listed them in, which made the default kernel arbitrary instead of the
newest one. Stamp the sort key along with the title.

crates/boot/src/main.rs

@@ -271,8 +271,9 @@ fn run() -> Result<()> {
             .freeze();
         // Provide the new context to the bootable entry.
         entry.swap_context(context);
-        // Restamp the title with any values.
+        // Restamp the title and sort key with any values.
         entry.restamp_title();
+        entry.restamp_sort_key();
 
         // Mark this entry as the default entry if it is declared as such.
         if let Some(ref default_entry) = config.options.default_entry {