Review embedded Activity themes

[bychkovdmitry]

Context & proposal

Currently embedded activities in UI Components like gallery Activity show purple status bar. Activities in Compose don't have explicit themes at all. That means that if a client has application theme with toolbar our ImagePreviewActivity will show two toolbars. We need to specify themes explicitly not to rely on the inherited app theme.

Also, clients should be aware how to override a theme. E.g.:

<activity
       android:name="io.getstream.chat.android.compose.ui.attachments.preview.ImagePreviewActivity"
       android:theme="@style/Theme.MaterialComponents.DayNight.NoActionBar"
       tools:replace="android:theme"
/>

We need to improve the themes that we use for activities in our SDKs.

Acceptance criteria

To accept this task we need to complete the following items:

• [ ] All embedded activities in UI Components specify theme explicitly
• [ ] All embedded activities in Compose specify theme explicitly
• [ ] UI Components Activities have reasonable status bar colors in both light and dark modes
• [ ] Compose Activities have reasonable status bar colors in both light and dark modes

[filbabic]

We can work on the small "guide" as a separate ticket.