docs: document patch rules

docs: document patch rules

Add a document to describe the rules for sending a proper patch.

As it contains all the information already being present in
docs/process/tags.pandoc remove that file.

The "Reviewed-by:" and "Acked-by:" tags are expanded to allow an
optional restriction of the tag.

A new tag "Origin:" is added to tag patches taken from another project.

Signed-off-by: Juergen Gross <jgross@suse.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>