Support per-component/architecture Release files

[tilmanKranz]

Is your feature request related to a problem? Please describe.

Certain installers, namely ubiquity and debian-installer (see [1]) "cross-validate" the architectures provided by deb-repositories by checking if the binary sub directories contain files named "Release" (i.e. $DIST/$COMPONENT/binary-$ARCH/Release). Most if not all upstream deb-repositories provide such files (see for example [2]).

[1] https://salsa.debian.org/installer-team/choose-mirror/-/blob/master/choose-mirror.c?ref_type=heads#L877
[2] http://archive.ubuntu.com/ubuntu/dists/noble/main/binary-amd64/

debian-installer will not work with repositories mirrored by "pulp-deb", because they do not pass the test in [1]; a DEBUG level error "architecture not supported by selected mirror" will be emitted.

Describe the solution you'd like

The proposed solution is to generate and publish such per-architecture Release files. An implementation is proposed here:

[3] main...b1-systems:pulp_deb:main#diff-07d1894abb8c46c901e374fbf6db5aff454975bc1d68a33aa81fdf96c379f419

Describe alternatives you've considered

Do not implement the proposed change.

Additional context

None.