Read \loader\loader.conf from the partition Sprout was loaded from and
use its default and timeout as the lowest priority source. Sprout now
picks the timeout in this order: LoaderConfigTimeoutOneShot,
--menu-timeout, the configuration, LoaderConfigTimeout, loader.conf. The
default entry order is the configuration, LoaderEntryDefault, loader.conf,
and a source that matches no entry falls through to the next one.
To tell an explicit menu-timeout from the built-in default, the
configuration option is now optional. Existing files are unaffected.
A loader.conf default of @saved selects the entry in
LoaderEntryLastBooted and saves the booted entry there on every boot.
After consuming a boot counter try, publish the renamed entry file in
LoaderBootCountPath and advertise the boot counting and saved entry
features.