rubocop: separated a common YaST style

Same content as for nfs-client
Once things stabilize it should move to devtools/buildtools.
rubocop: remove "Style/MultilineOperationIndentation" from the common part

See also 3cbfa31f472590c63bfbe23fef4506e3b505778e
This commit makes Rubocop pass again while highlighting the difference
in style to nfs-client.
Hopefully we can agree on a common style soon.