Task/change reg purpose frontend/2169

[andrea-williams]

Notes on Brianna's additions:

• The errors @andrea-williams was encountering were related to mocking. Even though the mocks were set up correctly, vitest wasn't picking them up (logged them in the code and they came out as real functions instead of spys). Vitest can be touchy about mocking the same file/function more than once, and I think our two fetchFormEnums helpers (one in admin, one in reg) were colliding with each other
• To address ^, I moved all the mocks that were used in fetchFormEnums to the shared bciers mocks/global files
• I also combined the two separate fetchFormEnums into a single function in the shared bciers file. The admin/reg returned different mock values, so I added an App arg so I could keep the different mock values without refactoring any tests