update ipxe image to use UEFI

[chrisjsimpson]

Is your feature request related to a problem? Please describe.
Currently we build a BIOS based IPXE image.

Describe the solution you'd like
Switch to a UEFI image.

Describe alternatives you've considered

Additional context

server-bootstrap/.github/workflows/release.yml

Lines 80 to 86 in b7d2b41

	echo Build iPXE ISO
	make \
	DEBUG=tls,httpcore,x509,certstore \
	CERT=ca.pem,isrgrootx1.pem,lets-encrypt-r3.pem \
	TRUST=ca.pem,isrgrootx1.pem,lets-encrypt-r3.pem \
	bin/ipxe.iso \
	EMBED=script.ipxe