To minimize the number of arguments passed to `lzbt`, the loader config
is assembled outside `lzbt` and passed as a single argument.
Instead of reimplementing `consoleMode` under the `lanzaboote`
namespace, `config.loader.systemd-boot.consoleMode` is reused as is.
The process of installing systemd-boot is "smarter" because it now
considers a a few conditions instead of doing nothing if there is a file
at the deistination path. systemd-boot is now forcibly installed (i.e.
overwriting any file at the destination) if (1) there is no file at the
destination, OR (2) a newer version of systemd-boot is available, OR (3)
the signature of the file at the destination could not be verified.
Julian Stecklina