Improve tests for lower port

[oliverfunk]

Description of issue / requirement to address

More and better tests are needed for the lower port duct.
The designer and builder were thoroughly tested during development, currently, however, only the angle of the duct is tested is unit tested.

It's a complex challenge writing tests that capture validly between in the input params and the output, hence this issue.

Some tests that could be implemented:

• Does the xz KOZ match an xz slice of the output xyz cad?
• Is the width and height of the port correct?
• Is the tf_offset correctly applied? Does the angled duct end at the correct place?
• Is the tf_thickness correctly taken into account when designing the angled extrude face?

[oliverfunk]

LInked PR #2108