BIOS: Prioritize image enumeration

Launch console BIOS is de-prioritized due to bugs.
Late PAL is de-prioritized due to additional regional checks that break import booting without fast boot.
PS2 is de-prioritized due to requiring a dynamic fast boot patch.
PS2 PAL is further de-prioritized due to additonal region checks.

src/core/bios.h

@@ -41,6 +41,7 @@ struct ImageInfo
   ConsoleRegion region;
   Hash hash;
   FastBootPatch fastboot_patch;
+  u8 priority;
 
   bool SupportsFastBoot() const { return (fastboot_patch != FastBootPatch::Unsupported); }