fix(dracut.sh): use dynamically uefi's sections offset

fix(dracut.sh): use dynamically uefi's sections offset

* Uefi section are creating by `objcopy` with hardcoded sections
offset. This commit allow to have the correct offset between
each part of the efi file, needed to create an UKI. Offsets
are simply calculated so no sections overlap, as recommended
in  https://wiki.archlinux.org/title/Unified_kernel_image#Manually
Moreover, efi stub file's header is parsed to apply the correct
offsets according the section alignment factor.
* Remove EFI_SECTION_VMA_INITRD, no need anymore as initrd
section offset dynamically calculated

Fixes dracutdevs#2275

Signed-off-by: Valentin Lefebvre <valentin.lefebvre@suse.com>