Set required GODEBUG flags for Go 1.23+

Related to gitlab-shell!1275 (comment 2481065330) and &17700 (closed)

We should set 'GODEBUG' => "tlskyber=0" (for Go 1.23) and 'GODEBUG' => "tlsmlkem=0" (for Go 1.24+) flags by default so that we don't have to set it in omnibus-gitlab and CNG and track it in two places. Doing it in labkit will cover all of our installation methods, including self compiled.