[Code health] Set up end to end testing (local web, mobile, and database emulation)

[sufyanAbbasi]

Formulating an overall strategy to run end to end testing on the mobile and web app. Will need to configure something like Docker or Github Hosted Runners which will spin up a local web server + Selenium WebDriver, local Android emulator + app, and a set up local Firebase database/emulator then run through a set of core tests.

[sufyanAbbasi]

Mirror: https://github.com/google/ground-platform/issues/1699

[sufyanAbbasi]

TODOs:

• [ ] Fix broken sign-in procedure on emulator (the USE_EMULATOR flag should prevent the sign-in page from showing up)
• [ ] Add additional test coverage for other CUJs like offline imagery
• [ ] Add test coverage for Android lifecycle issues like screen rotation.