SG-209 Account switching in autofill UI (Android)

[mpbw2]

Type of change

• Bug fix
• New feature development
• Tech debt (refactoring, code cleanup, dependency upgrades, etc)
• Build/deploy pipeline (DevOps)
• Other

Objective

Added support for account switching within the autofill UI on Android

Code changes

• AutofillCiphersPage.xaml: Added AvatarImageSource to toolbar, additional ShowNoData property (explained below), and AccountSwitchingOverlayView control to layout
• AutofillCiphersPage.xaml.cs/AutofillCiphersPageViewModel.cs: Added avatar & overlay support, plus separate loading & "NoData" states to smooth out UX when switching accounts (previously "NoData" was simply the negated "HasData" resulting in "No Matches" being shown momentarily before showing the matches)
• App.xaml.cs: Added additional condition for clearing Options.Uri upon exiting the autofill flow (required to prevent main app from falling back into "autofill matches" view when switching accounts, as that triggers the SetMainPageAsync() flow that shows autofill matches if Options.Uri has value)

Testing requirements

Testing should consist of three parts:

1. Obvious: Trigger autofill, switch users, unlock if necessary, select matches
2. Less Obvious: Make sure main app continues to behave normally after using autofill flow (including saving new creds during autofill)
3. Not Remotely Obvious: File selection flow (via file attachments and file Sends)

Before you submit

• I have added unit tests where it makes sense to do so (encouraged but not required)
• This change requires a documentation update (notify the documentation team)
• This change has particular deployment requirements (notify the DevOps team)

[vvolkgang]

LGTM!