[3.29] feat: drop MySQL and SQLServer support
see https://forge.extranet.logilab.fr/cubicweb/cubicweb/-/jobs/269972 for !229 (merged)
--HG-- branch : 3.29
see https://forge.extranet.logilab.fr/cubicweb/cubicweb/-/jobs/269972 for !229 (merged)
--HG-- branch : 3.29