tree-wide: Drop gnu-efi

This drops all mentions of gnu-efi and its manual build machinery. A
future commit will bring bootloader builds back. A new bootloader meson
option is now used to control whether to build sd-boot and its userspace
tooling.

test/meson.build

@@ -73,7 +73,7 @@ if install_tests
                                  '../-.mount',
                                  testsuite08_dir + '/local-fs.target.wants/-.mount')
 
-        if conf.get('HAVE_GNU_EFI') == 1 and conf.get('HAVE_ZSTD') == 1
+        if conf.get('ENABLE_BOOTLOADER') == 1 and conf.get('HAVE_ZSTD') == 1
                 install_subdir('test-bcd',
                                exclude_files : '.gitattributes',
                                install_dir : testdata_dir)

test/mkosi.default.networkd-test

@@ -33,8 +33,6 @@ BuildPackages=
         gcc
         gettext
         git
-        gnu-efi
-        gnu-efi-devel
         gnutls-devel
         gperf
         hostname