The current PXE loader does not work since it became too big. This change creates a dedicated loader for use when booting over PXE, with support removed for the FAT and EXT2 filesystems, as well as for GZIP and BZIP2 compression. This new loader still defaults to the same interpreter as the regular loader.
It is then possible to boot the kernel over TFTP or NFS again.
This is meant as a possible alternative to D41750, and relevant to PR #257018.