Suite: Fix problems on Blazor UI generation (missing enum namespace, and nullable annotation) #16435
Description
Resolves #16430, resolves #16434
Checklist
- I fully tested it as developer / designer and created unit / integration tests
- I documented it (or no need to document or I will create a separate documentation issue)
- I worked with the design team to get their idea for UI/UX design (or no need to design for this PR)
- I've assigned reviewer, related labels and set a milestone for this PR