Use PlatformContext to pass Android Activity Context to use cases

[cbeyls]

Since many use cases should use an Activity Context rather than the Application Context on Android to work properly (mostly to launch Intents), refactor these use cases to take a PlatformContext argument and use it to wrap the Android Context on Android.

• Move PlatformContext from the ui module to the domain module so it can be referenced from use cases.
• Define PlatformContext as an empty object on iOS and a class containing a Context reference on Android.
• Replace LocalPlatformContext CompositionLocal with an expect getPlatformContext() composable function. There is no need to create a new CompositionLocal because Android already has LocalContext to carry the Context over to any composable function, and an expect function is safer because it guarantees that a non-null PlatformContext is provided for every platform at compile time.
• Update UrlOpener, OpenMapUseCase, ApplyForAppClinicUseCase, OpenCocUseCase, OpenFaqUseCase, OpenLinkUseCase, OpenPartnerLinkUseCase, OpenXAccountUseCase, OpenXHashtagUseCase, OpenYoutubeUseCase, ShareSessionUseCase to accept a PlatformContext as first argument.
• Update the Android implementation of ShareSessionUseCase to use ShareCompat.IntentBuilder from the androidx.core library.
• Use safer Uri.Builder instead of custom String formatting to build map Uri.

[martinbonnin]

Replace LocalPlatformContext CompositionLocal with an expect getPlatformContext() composable function.

Much better 👍 . Also another use case for expect/actual classes.