[Forms] Required fields should be explicitly indicated, not implicitly indicated by not having "optional" text

[billhimmelsbach]

During our accessibility review, the reviewer was concerned that our CFPB DS guidance on labeling only optional fields led to confusion and wasn't in line with common form expectations. She suggested adding * and legends describing that * meant required, which is very common, but we made a compromise that we could describe what was required in form descriptions and fieldsets. But going forward, we'd want a consistent approach across all forms.

Current behavior

• only optional fields are marked

Expected behavior

• required fields are indicated explicitly