[dvgen] generating testbench w/in Ubuntu container but simulating in CentOS

### Description

My company standardizes on CentOS. I've got a Docker container with Ubuntu running and Verilator tests run.
But Siemens tools are not supported on Ubuntu, and I've got a complete regression grid on CentOS.
Opentitan has lots and lots of documentation - and I've been reading them - but it's not clear to me how to get the testbench (only) generated for Questa targetted to an arbitrary directory.

NOTE: I have the same problem for Vivado and static/formal - lots of resources available on CentOS.

Start by reviewing the existing OpenTitan documentation for Questa, Vivado, and static/formal flows, then identify how testbench generation is separated from simulation. Document a supported Ubuntu-container workflow that writes the generated Questa testbench to an arbitrary directory for use on CentOS, and clarify whether the Vivado and static/formal cases are covered as well.

Written by the indexing model from the issue text.