Some firmware signals the key event without a key being available. The
simple menu then skipped the countdown for that tick, and the basic menu
started waiting for the full timeout again, so firmware that kept
signaling the key event would never boot the default entry.
Read the key inside the wait, and when no key is available keep waiting
on the same timer.
The basic menu set a single timer for the whole timeout, and converting
a timeout of more than about 1.8e12 seconds into 100ns timer units
panics. The timeout can come from --menu-timeout or from
LoaderConfigTimeout, which persists, so the panic would repeat on every
boot. Limit a single timer to u32::MAX seconds.
The boot menu is now a BootMenu trait with two styles. The basic menu is
the existing one that prints entries and selects them by number. The new
simple menu is full-screen: entries are centered and highlighted, the
arrow keys, home, end, page up and page down move the selection, enter
boots it, and any key stops the countdown.
The style is picked with --menu-style or menu-style in [options], and
defaults to simple. The timer code used to wait for a key is shared
between both menus in menu.rs.
Some firmware signals the key event without a key being available.
This previously aborted boot with "no key was pressed"; treat it as a
no-op and keep waiting instead.
alex