What kind of change does this PR introduce?

mainly: run supabase_flutter test on web
but I've noticed several other issues and fixed them as well

What is the current behavior?

We only test for the vm version, but not the web version. We do build the example app for web, but this does not catch runtime errors.

What is the new behavior?

• Run the supabase_flutter tests on chrome in js and wasm mode.
• Fix running analyzer and formatting for supabase_flutter in ci
• Therefore, fixed some lint diagnostics in the supabase_flutter example app
• Migrate the web localstorage implementation to web package (continue feat(gotrue, supabase, supabase_flutter, realtime_client): Use web package to access web APIs #1135)

Additional context

For now, I've only added it to ci for supabase_flutter as I'm somehow not able to do http requests. Neither to localhost nor to something like google. I'm pretty sure CORS is not the reason, but I couldn't find the reason.