[boot] Load programs in boot, not kernel

Remove ELF and initrd loading from the kernel. The bootloader now loads
the initial programs, as it does with the kernel. Other files that were
in the initrd are now on the ESP, and non-program files are just passed
as modules.

src/boot/memory.h

@@ -30,8 +30,8 @@ constexpr uefi::memory_type args_type =
 constexpr uefi::memory_type module_type =
 	static_cast<uefi::memory_type>(0x80000001);
 
-/// Memory containing loaded kernel code and data sections
-constexpr uefi::memory_type kernel_type =
+/// Memory containing loaded kernel or program code and data sections
+constexpr uefi::memory_type program_type =
 	static_cast<uefi::memory_type>(0x80000002);
 
 /// Memory containing page tables set up by the loader