Fix StrictMode violations in the AttachmentsPicker

[VelikovPetar]

🎯 Goal

Implements fixes for StrictMode violations (Read/Write disk on main thread) originating from the attachments picker.
Resolves: https://linear.app/stream/issue/AND-938/fix-strictmode-violations-in-attachmentspicker

🛠 Implementation details

• Introduce new AttachmentsProcessingViewModel which defers the StorageHelperWrapper operations to a background thread.
• Use the new view model in AttachmentsPickerFilesTabFactory, AttachmentsPickerImagesTabFactory and in AttachmentsPickerSystemTabFactory
• Add similar async operations in the AttachmentsPickerViewModel
• Rework the AttachmentsPicker composable to use the new asynchronous methods

🎨 UI Changes

NA

🧪 Testing

1. Open attachment picker
2. Select from the Images or Files tab (or do the same with ChatTheme(useDefaultSystemMediaPicker = true))
3. There should be no violations logged in the LogCat

[github-actions]

SDK Size Comparison 📏

SDK	Before	After	Difference	Status
stream-chat-android-client	5.25 MB	5.25 MB	0.00 MB	🟢
stream-chat-android-offline	5.48 MB	5.48 MB	0.00 MB	🟢
stream-chat-android-ui-components	10.59 MB	10.59 MB	0.00 MB	🟢
stream-chat-android-compose	12.81 MB	12.82 MB	0.01 MB	🟢

[sonarqubecloud]

Quality Gate failed

Failed conditions
43.6% Coverage on New Code (required ≥ 80%)

See analysis details on SonarQube Cloud