fix: Move files in /usr/etc to /etc

[KyleGospo]

Adding files to /usr/etc is considered undefined behavior

[castrojo]

Ok I've removed all mentions of the etc-merge service. Please doublecheck my work.

[castrojo]

This good to go or are we still sorting out that containers.json thing? (Does that even affect Bluefin since we're not using the rechunker?)

[p5]

This good to go or are we still sorting out that containers.json thing? (Does that even affect Bluefin since we're not using the rechunker?)

@castrojo The containers.json thing is only affecting main and ucore since this is where we add the container policy to the image by installing the ublue-is-signing RPM.

The issue there is we want to move the policy from /usr/etc to /etc, but Fedora's containers package already has taken "ownership" of that file, and doesn't allow us to overwrite it from our own RPM.

This has been reverted in ublue-os/config for now but I don't think we have any issues here.