Add configuration signals for i22 fswitch

[joeshannon]

To match the Nexus file requirements, further fields should be available for the fswtich. These are effectively static metadata and can be implemented using ConfigSignal.

The required data is:

• lens_geometry (NX_CHAR) - paraboloid
• cylindrical (NX_BOOLEAN) - 1
• lens_material (NX_CHAR) - Beryllium

These are in addition to number_of_lenses (NX_INT) which is already implemented

Acceptance Criteria

• Signals added as children to i22's fswitch device
• Existing test updated to confirm these fields are present