UI: Consolidate Host, Platform, Strata Interfaces/types/formatting utils into Base Layer

Currently, for Examiners App is only extending the Base Layer. So to utilize application interfaces from Host, Platform, Strata, they had to be manually copied over to `examiners-web-app`. This creates duplication and lack of consistency if any of those interfaces is changed in the original respective application.

So the proposed tasks are:
- [ ] Move Host, Platform, Strata Interfaces to Base Layer
- [ ] Remove duplicate interfaces from Examiner app
- [ ] Use Host, Platform, Strata from the Base Layer in Examiner app