Refactor SPA framework code:

1. rename framework/api folder to framework/common
2. rename SettingsPageRepository to SettingsPageProviderRepository
3. rename spa/MainActivity to spa/BrowseActivity
4. Add SpaEnvironment for all environment related setup for gallery

Bug: 244122804
Test: manual - build Spa gallery
Test: refactoring CL. Existing unit tests still pass.

Change-Id: I81fb60e46ef19b5176a4c2fa6e67a4f2bf0e328c