element-android warn on cross signing reset

Type of change

[x] Bugfix

Content

Fixes #6702 Parity with web. Show a warning when a previously verified user rotated his cross signing keys.

We now remember locally when a user was verified once. When/If that user rotate his cross signing keys he will be marked with a red shield instead of black shield.

Requires a database migration to remember that the user was verfied once
Refactoring: The shield state of users was using the same enum as rooms RoomEncryptionTrustLevel, now I introduced a new enum for users UserVerificationLevel that is used in UI to decorate avatars.

Motivation and context

Screenshots / GIFs

Tests

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Tested devices

[ ] Physical
[x] Emulator
OS version(s):

Checklist

[x] Changes has been tested on an Android device or Android emulator with API 21
[x] UI change has been tested on both light and dark themes
[x] Accessibility has been taken into account. See https://github.com/vector-im/element-android/blob/develop/CONTRIBUTING.md#accessibility
[x] Pull request is based on the develop branch
[x] Pull request includes a new file under ./changelog.d. See https://github.com/vector-im/element-android/blob/develop/CONTRIBUTING.md#changelog
[ ] Pull request includes screenshots or videos if containing UI changes
[x] You've made a self review of your PR
[ ] If you have modified the screen flow, or added new screens to the application, you have updated the test UiAllScreensSanityTest.allScreensTest()