Add memory_id program to set properties about the physical memory
devices in the system. This is useful on machines with removable memory
modules to show how the machine can be upgraded, and on all devices to
detect the actual RAM size, without relying on the OS accessible amount.
Closes: #16651
Concatenating strings is not a very efficient approach. And in this case fully
unnecessary. We also need some rules to make use of those hwdb entries.
PCI needs to be 8 characters, not 4. And we need to use uppercase hexadecimal
for both. With udev rules this made no difference, but hwdb match is case
sensitive.
Fixes#16119.
This change is only about the source tree. We have tmpfiles.d/, modprobe.d/,
sysctl.d/, and sysusers.d/, but for historical reasons, rules/ didn't fit this
pattern. We also *install* it as rules.d/. Let's rename to be consistent.