Add StepExpansion geometry on FE meshes

[amal-ghamdi]

Description:

Add support for step expansion in 1D and 2D from FE meshes. This feature is needed by the Wolfgang Bangreth elasticity benchmark.

DoD:

• [ ] A class StepExpantion with a docstring example is added
• [ ] tests are added
• [ ] PR is approved

Note:

The PR is created by @Naokikiki and updated by @amal-ghamdi

[amal-ghamdi]

@jakobsj , I appreciate it if you could look at the DoD, thank you.