Partials: Update partials/attributes for newer Antora versions
This commit updates where the attributes.adoc file is stored (a.k.a.
Antora partials). It also updates the `include::` header in all AsciiDoc
files to explicitly use partials included in the `ROOT` module of the
project.
More information:
https://docs.fedoraproject.org/en-US/fedora-docs/asciidoc-fedora/reusable-attributes/
Signed-off-by: Justin W. Flory (he/him) <git@jwf.io>