Add the HCAL demonstrator into the `ldmx-reduced-v2`

[tvami]

Is your feature request related to a problem? Please describe.

Currently ldmx-reduced-v2 has the full HCAL.

Describe the solution you'd like

We already have a demonstrator geometry, I'd like to have that added to the ldmx-reduced-v2, I'm sure somebody with more HCAL knowledge could this quickly.

Describe alternatives you've considered

I think we have to do this for the reduced-LDMX tests coming up