Add fsd_v23a geometry

Please insert x between square brackets to tick the boxes, add a meaningful description if the title is not enough and check the outcome with the "Preview" tab

In case you committed a new geometry:

• Ran the scripts for materials and radiation length check on my new geometry file? (and read carefully the output of course)

  bash ci_scripts/check_radlen.sh <path>/<file>.geo.root

• Added also the corresponding creation macro?
• Checked that the geometry does not contains unexpected overlaps, e.g. either at end of the creation macro or with the something similar to the mCBM macro
  macro/mcbm/mcbm_check_overlaps.C

In case you committed a new setup file:

• Checked that all geometries listed are present in the repository?
• Ran the CBMROOT macro/geometry/check_media.C on the corresponding .geo.root file? (output by the transport macro)