boot: Change boot entry sorting

boot: Change boot entry sorting

There are a few undesirable properties to how boot entries are
currently sorted.

First, it sorts by entry file name only, which may not correspond
to the title that is shown (for exmaple because it is prefixed by
machine-id). The file ending will also create unexpected ordering
("arch-lts.conf" would come before "arch.conf").

While the list is sorted alphabetically ascending, it is also
lower version/priority first, which is unintuitive. In particular,
a boot-counted entry that is bad (0 tries left) will be at the very
top.

Additionally, the Windows and Mac loaders should be sorted with
the rest of the loaders.