tgt: Install systemd tgtd.service (#65565)

* tgt: Add homepage

* tgt: tgt-admin needs lsof, sg3_utils and tgtadm

Otherwise it fails with return code 72057594037927935.

* tgt: libxslt and docbook_xsl not needed at runtime

They're only there to build the documentation.

* tgt: Install systemd tgtd.service

Resolves #38012

* tgt: Add JohnAZoidberg as maintainer